ARCIU · Archimedes Tech SPAC Partners III Co. · Holdings

$10.24 At close · Oct 14

Market Cap

$354.03M

35.26M

Volume · Oct 14 400 Avg daily vol (13 sessions) 9004

Institutional ownership from SEC Form 13F filings. Investment managers with more than $100 million in U.S. equities must disclose their positions every quarter, within 45 days of quarter-end, so the holdings shown can lag the market by up to a quarter.

Use institutional holdings through the 13F API or MCP → See every holder of ARCIU: 13F, 13D and 13G, insiders and funds →

Institutional holdings are being reconciled with SEC filings. Holder totals and changes may be incomplete until reconciliation finishes.

Quarter:

Holders: 15

Total Value: $47,129,389

Total Shares: 4,625,063

Institutional Ownership Trend

2 quarters

Holder Concentration

Across 15 13F filers · Δ vs Mar 31, 2026

Top Holder

27.0%

+13.3 pts

Top 5

74.1%

+28.4 pts

Top 10

96.1%

+25.4 pts

HHI

1,419

Broadly held+761

Who Holds ARCIU

Last 2 quarters through Jun 30, 2026

Each kind of 13F filer's share of the common shares 13F filers report. Holder type comes from regulatory records, never the filer's name; style, turnover and horizon are measured from each filer's own 13F book. The quarter selector does not change this card.

Jun 30, 2026: 15 filers, like-for-like change -49.2%; actively managed books -49.2%; index-like books +7.7%.

Holder type	Share	Filers	Change	New	Exited
Registered adviser	31.9%	7	-63.1%	1	9
Exempt adviser	30.3%	2	0.0%	0	0
Bank	14.0%	1	+158.5%	0	0
Benefit plan	10.4%	1	0.0%	0	0
Non-US	0.0%	0	-100.0%	0	3
Unknown	13.5%	4	-53.0%	0	3

Style	Share	Filers	Change	New	Exited
Index-like	0.2%	1	+7.7%	0	0
Systematic-like	48.2%	4	-31.5%	0	4
Concentrated	6.7%	2	+1.4%	0	1
Diversified active	44.9%	8	-62.5%	1	10

Turnover	Share	Filers	Change	New	Exited
Low turnover	2.7%	1	-76.3%	0	1
Medium turnover	35.4%	5	-55.7%	1	5
High turnover	54.9%	7	-44.4%	0	8
Unknown	7.0%	2	+5.9%	0	1

Holding horizon	Share	Filers	Change	New	Exited
Short horizon	15.6%	6	-66.6%	1	5
Medium horizon	35.7%	2	-15.3%	0	1
Long horizon	30.9%	4	-31.8%	0	2
Unknown	17.8%	3	-71.5%	0	7

13F book size	Share	Filers	Change	New	Exited
Under $1B	6.5%	2	-48.3%	0	4
$1B to $10B	44.0%	5	-51.5%	1	6
$10B to $100B	45.6%	7	-39.3%	0	4
$100B or more	3.9%	1	-78.7%	0	1

Client base	Share	Filers	Change	New	Exited
Pooled investment vehicles	26.8%	4	-59.1%	1	6
Registered funds and BDCs	5.1%	3	-70.7%	0	2
Other investment advisers	0.0%	0	-100.0%	0	1
Unknown	68.1%	8	-38.2%	0	6

Private funds	Share	Filers	Change	New	Exited
Hedge funds	30.1%	5	-62.2%	1	7
Private equity funds	0.0%	0	-100.0%	0	1
Other private funds	2.7%	1	0.0%	0	0
Private funds, type not stated	27.0%	1	0.0%	0	0
No private funds	2.4%	2	-37.6%	0	1
Unknown	37.8%	6	-52.7%	0	6

Location	Share	Filers	Change	New	Exited
United States	39.4%	10	-65.0%	1	11
Outside the US	60.6%	5	-28.1%	0	4

How the mix is measured

Shares are 13F common shares restated to today's split basis; options and principal amounts are left out. The change compares only filers with a 13F in both quarters and keeps each filer in its bucket of the later quarter on both sides; a filer that continues under a new CIK is compared through its successor. Holder type comes from each filer's current regulatory profile; client base and private funds come from the Form ADV roster current at each quarter end (rosters from December 2019, so an earlier quarter reads Unknown). Style, turnover, horizon and book size are measured from each filer's 13F book in the newest measured quarter, and Not measured means none was. Actively managed books are those measured systematic-like, concentrated or diversified active.

Conviction and Crowding

15 13F filers, quarter ended Jun 30, 2026

Measured across every 13F filer's common-share book once the quarter's filing window closed. Crowding counts filers with high turnover or that advise private funds on Form ADV.

Conviction holders

0.000% of filers hold it in their top 10

Mar 31, 2026: 0

Holders above 5%

median weight 0.030%

Mar 31, 2026: 0

Crowding

—

shares outstanding is an issuer-wide count, not one listing's

Private-fund advisers

—

of shares outstanding

Institutional ownership

—

shares outstanding is an issuer-wide count, not one listing's

Top 10 holders

96.1%

of 13F shares, Herfindahl 0.142

Active holders

-49.2%

like-for-like share change of active filers

5% stakes on record

0 13D, 0 13G

How long holders have held it value-weighted 2.0 quarters

Under 1 year 100.0% 1 to 3 years 0.000% 3 years or more 0.000% Since coverage start 0.000%

Managers in the top fifth by current three-year FundScore alpha were net buyers of $0 (0 buying, 0 selling).

Estimated Holder Cost Basis

Quarter ended Jun 30, 2026, on that quarter's share basis

Estimated, never filed: each 13F buy is costed at its quarter's average traded price and each sale keeps the average cost, so this is what holders paid on average if they traded evenly through each quarter.

Estimated avg cost

$10.05

estimated per share

Mar 31, 2026: $10.05

Quarter-end price

$10.19

implied by 13F values

Estimated gain or loss

+1.4%

price against the estimated cost

Estimated at a loss

0.000%

of costed 13F value

Estimated cost covers 100.0% of the 13F shares; positions already held when a filer's 13F history starts, or bought in a quarter without a trusted average price, have no estimate.

Shared Holders

Companies ARCIU's active holders also own, quarter ended Jun 30, 2026

#	Company	Shared holders	Similarity
1	SORN Soren Acquisition Corp.	4	0.632
2	FMAC Future Money Acquisition Corp	4	0.596
3	SAAQ Space Asset Acquisition Corp.	4	0.596
4	KRAQ KRAKacquisition Corp	3	0.548
5	IACO Idea Acquisition Corp.	4	0.539
6	ALOV Aldabra 4 Liquidity Opportunity Vehicle, Inc.	3	0.507
7	ADAC American Drive Acquisition Co	3	0.447
8	FTHA Forefront Tech Holdings Acquisition Corp	3	0.447
9	IEAG Infinite Eagle Acquisition Corp.	3	0.447
10	HACQ HCM IV Acquisition Corp.	3	0.447

Shareholder Targets

13F filers that own its peers but not ARCIU, quarter ended Jun 30, 2026

Found through its holder-overlap peers: SORN, FMAC, SAAQ, KRAQ, IACO, ALOV, ADAC, FTHA, IEAG, HACQ, IGAC, GCGR, YCY, QLEP, RNGT, COPL, AIIA, EVAC, APMC, JENA. 73 filers in all.

#	Filer	In peers	Of book	Largest peers
1	HGC Investment Management Inc. Non-US, Diversified active	$56,651,599 7 held	18.8%	ALOV, KRAQ, GCGR
2	Sculptor Capital LP Registered adviser, Diversified active	$55,950,253 6 held	0.900%	GCGR, KRAQ, APMC
3	Karpus Management, Inc. Adviser, Diversified active	$54,619,895 7 held	1.72%	AIIA, COPL, FMAC
4	HIGHBRIDGE CAPITAL MANAGEMENT LLC Registered adviser, Diversified active	$50,877,353 13 held	3.06%	COPL, FMAC, HACQ
5	MIZUHO SECURITIES USA LLC Unknown, Index-like	$36,446,364 13 held	0.570%	COPL, FMAC, YCY
6	Empyrean Capital Partners, LP Registered adviser, Diversified active	$35,349,880 2 held	1.34%	GCGR, IEAG
7	Fort Baker Capital Management LP Registered adviser, Concentrated	$33,949,720 4 held	3.43%	SAAQ, GCGR, EVAC
8	HEIGHTS CAPITAL MANAGEMENT, INC Unknown, Diversified active	$25,221,826 14 held	7.17%	GCGR, COPL, AIIA
9	Jain Global LLC Registered adviser, Systematic-like	$24,472,418 4 held	0.310%	KRAQ, EVAC, ALOV
10	Kryger Capital LLC Registered adviser, Concentrated	$24,230,127 6 held	1.59%	ALOV, HACQ, SAAQ

Fund Ownership of ARCIU by Fund Type

Registered funds' Form N-PORT reports for the quarter ended Jun 30, 2026

Index funds and index ETFs hold 0 shares.

Fund type	Shares	Funds
Index funds	0	0
Index ETFs	0	0
Active ETFs	10,769	1
Active funds	20,000	1
Unclassified	0	0
All registered funds	30,769	2

How fund types are measured

Each fund series counts once, with its latest Form N-PORT report dated inside the quarter; only long share positions count, restated to today's split basis. The fund type is the series' latest Form N-CEN answer on or before the quarter end (the index-fund box and the exchange-traded flag), never its name. Unclassified funds have no usable N-CEN; unit investment trusts are among them, so index ownership is a floor. Funds sit inside their advisers' 13F reports, so these shares overlap the 13F figures and are never added to them.

Quarterly Activity

vs Mar 31, 2026

New

Increased

Decreased

Sold Out

Unchanged

New and Sold Out count only filers that reported a 13F for both quarters: a first-time filer's book is not a buy, and a fund that has not filed, or withheld its positions under confidential treatment, has not sold.

Holder count: -14

Institutional value: -48.2%

Shares held: -49.2%

Top Buyers

vs Mar 31, 2026

Institution	Added	Now Holds
Large TORONTO DOMINION BANK	+396,217	646,217
Large Clear Street Group Inc.	+24,194	34,256
Small Lineage Point Capital LP	+13,776	288,776
Mid ARISTEIA CAPITAL, L.L.C.	+989	400,779
Small Tuttle Capital Management, LLC	+769	10,769

Top Sellers

vs Mar 31, 2026

Institution	Sold	Now Holds	Open
Mega MILLENNIUM MANAGEMENT LLC	−170,257	179,743

Top New Positions

vs Mar 31, 2026

Institution	Acquired	Value (USD)	Open
Mid GLAZER CAPITAL, LLC	10,523	$107,229

Top Sold-Out Positions

vs Mar 31, 2026

Institution	Previously Held	Last Value (USD)
Large Alberta Investment Management Corp	1,000,000	$10,000,000
Mid AQR Arbitrage LLC	757,625	$7,576,250
Mid RIVERNORTH CAPITAL MANAGEMENT, LLC	500,000	$5,000,000
Mid Lighthouse Investment Partners, LLC	500,000	$5,000,000
Mega BNP PARIBAS ARBITRAGE, SA	492,375	$4,923,750

Filter: New 1 Increased 6 Reduced 1 Sold out 15 Unchanged 7

Holder type: Registered adviser 7 Exempt adviser 2 Bank 1 Benefit plan 1 Unknown 4

Showing 15 of 15

All Common Calls Puts

Compact Export CSV

Holder

Value (USD)

% of 13F

LMR Partners LLP ARCIU

$12,737,500

27.03%

1,250,000

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
LMR PARTNERS (DIFC) Ltd	1,250,000	$12,737,500	100.0%	Sole

TUDOR INVESTMENT CORP ET AL ARCIU

$6,623,500

14.05%

650,000

TORONTO DOMINION BANK ARCIU

$6,584,951

13.97%

646,217

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
TD SECURITIES (USA) LLC	573,517	$5,844,138	88.7%	Defined
Held directly	72,700	$740,813	11.3%	Sole

OMERS ADMINISTRATION Corp ARCIU

$4,891,200

10.38%

480,000

ARISTEIA CAPITAL, L.L.C. ARCIU

$4,083,938

8.67%

400,779

Lineage Point Capital LP ARCIU

$2,942,627

6.24%

288,776

BlueCrest Capital Management Ltd ARCIU

$2,802,250

5.95%

275,000

MILLENNIUM MANAGEMENT LLC ARCIU

$1,831,581

3.89%

179,743

Qube Research & Technologies Ltd ARCIU

$1,528,500

3.24%

150,000

Calamos Advisors LLC ARCIU

$1,263,560

2.68%

124,000

Westchester Capital Management, LLC ARCIU

$1,018,999

2.16%

100,000

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
WESTCHESTER CAPITAL PARTNERS, LLC	887	$9,038	0.9%	Sole
Virtus Investment Advisers, LLC	90,634	$923,560	90.6%	Other
Held directly	8,479	$86,401	8.5%	Sole

Clear Street Group Inc. ARCIU

$349,068

0.74%

34,256

HRT FINANCIAL LP ARCIU

$254,750

0.54%

25,000

Tuttle Capital Management, LLC ARCIU

$109,736

0.23%

10,769

GLAZER CAPITAL, LLC ARCIU

$107,229

0.23%

10,523

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
North Rock Capital Management, LLC	500,000	$5,000,000	100.0%	Defined

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
ABC ARBITRAGE ASSET MANAGEMENT joint	40,000	$400,000	100.0%	Other

Key facts CIK 2083910 CUSIP G0453R105 Visit website Investor relations