8-K

UNITED STATES

SECURITIES AND EXCHANGECOMMISSION

Washington, D.C. 20549

Form 8-K

Current Report

Pursuant to Section 13or 15(d) of the Securities Exchange Act of 1934

March 10, 2026

Date of Report (Date of earliest event reported)

Archimedes Tech SPACPartners III Co.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (725) 312-2430

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01. Other Events.

On March 10, 2026, Archimedes Tech SPAC Partners III Co. (the “Company”) announced that, on or about March 16, 2026, the holders of the Company’s units (the “Units”) may elect to separately trade the ordinary shares and warrants included in the Units. Each Unit consists of one ordinary share and one-fourth of one redeemable warrant. Any Units not separated will continue to trade on The Nasdaq Global Market (“Nasdaq”) under the symbol “ARCIU.” Any underlying ordinary shares and warrants that are separated will trade on Nasdaq under the symbols “ARCI” and “ARCIW,” respectively. Holders of Units will need to have their brokers contact Odyssey Transfer and Trust Company, the Company’s transfer agent, in order to separate the holders’ Units into ordinary shares and warrants.

A copy of the press release issued by the Company announcing the separate trading of the securities underlying the Units is attached hereto as Exhibit 99.1.

Item 9.01. Financial Statementsand Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: March 10, 2026

Exhibit 99.1

Archimedes Tech SPAC PartnersIII Co.

Announces the Separate Trading of its Ordinary Shares and Warrants

Commencing March 16, 2026

CLAYMONT, DE, March10, 2026 – Archimedes Tech SPAC Partners III Co. (Nasdaq: ARCIU) (the “Company”) today announced that, commencing March 16, 2026, holders of the units sold in the Company’s initial public offering may elect to separately trade the Company’s ordinary shares and warrants included in the units.

No fractional warrants will be issued upon separation of the units and only whole warrants will trade. The ordinary shares and warrants that are separated will trade on The Nasdaq Global Market under the symbols “ARCI” and “ARCIW,” respectively. Those units not separated will continue to trade on The Nasdaq Global Market under the symbol “ARCIU.” Holders of units will need to have their brokers contact Odyssey Transfer and Trust Company, the Company’s transfer agent, in order to separate the units into ordinary shares and warrants.

The offering of the units was made only by means of a prospectus, copies of which may be obtained from BTIG, LLC, 65 East 55th Street, New York, New York 10022, or by email at ProspectusDelivery@btig.com. The registration statements on Form S-1 (333-292419) and Form S-1MEF (File No. 333-292891) relating to these securities have been filed with the Securities and Exchange Commission (“SEC”) and became effective on January 22, 2026. Copies of the registration statements can be accessed through the SEC’s website at www.sec.gov.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Archimedes TechSPAC Partners III Co.

Archimedes Tech SPAC Partners III Co. is a blank check company, also commonly referred to as a special purpose acquisition company, or SPAC, formed for the purpose of effecting a merger, share exchange, asset acquisition, share purchase, recapitalization, reorganization or other similar business combination with one or more businesses. While the Company may pursue a business combination target in any business, industry or geographical location, the Company intends to focus its search for businesses in the technology industry, and its focus will be on the artificial intelligence, cloud services and automotive technology sectors.

Cautionary Note Concerning Forward-LookingStatements

This press release includes forward-looking statements that involve risks and uncertainties. Forward looking statements are statements that are not historical facts. Such forward-looking statements are subject to risks and uncertainties, which could cause actual results to differ from the forward-looking statements. The Company expressly disclaims any obligations or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in the Company’s expectations with respect thereto or any change in events, conditions or circumstances on which any statement is based. Forward-looking statements are subject to numerous conditions, many of which are beyond the control of the Company, including those set forth in the Risk Factors section of the registration statements and the prospectuses filed in connection with the initial public offering with the SEC. Copies are available on the SEC’s website, www.sec.gov.

Contact Information

Long Long

Chief Executive Officer

Archimedes Tech SPAC Partners III Co.

(725) 312-2430