美国锑公司美股招股说明书(2025-10-17版)

Up to $400,000,000 Common Stock We previously entered into a sales agreement dated November 12, 2024 and subsequently amended and restated such sales agreementon September 17, 2025 (the “Sales Agreement”), with A.G.P./Alliance Global Partners (“A.G.P.”) and B. Riley Securities, Inc. (“B.Riley Securities”; each an “Agent” and collectively, the “Agents”), relating to shares of our common stock, $0.01 par value per share,offered by this prospectus supplement and the accompanying prospectus. Pursuant to this prospectus supplement and accompanyingprospectus, from time to time we may offer and sell shares of our common stock having aggregate gross proceeds of up to$400,000,000 through or to the Agents, acting as sales agent or principal. Our common stock is listed on the NYSE American and the NYSE Texas, both under the symbol “UAMY.” The last reported saleprice of our common stock on October 13, 2025 was $16.71 per share. Sales of our common stock, if any, under this prospectus supplement may be made in sales deemed to be an “at the market offering” asdefined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended (the “Securities Act”). Subject to terms of theSales Agreement, the Agents are not required to sell any specific number or dollar amounts of securities but will act as our sales agentusing commercially reasonable efforts consistent with their normal trading and sales practices, on mutually agreed terms between theAgents and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement. The Agents will be entitled to compensation under the terms of the Sales Agreement at a commission rate of up to 3.0% of the grosssales price per share sold. In connection with the sale of our common stock on our behalf, the Agents will each be deemed to be an“underwriter” within the meaning of the Securities Act and the compensation of the Agents will be deemed to be underwritingcommissions or discounts. We have also agreed to provide indemnification and contribution to the Agents against certain civilliabilities, including liabilities under the Securities Act. See “Plan of Distribution” beginning on page S-11 for additional informationregarding the compensation to be paid to the Agents. Investing in our common stock involves risks. See “Risk Factors” on pageS-6of this prospectus supplement and in thedocuments incorporated by reference into this prospectus supplement and the accompanying prospectus before investing inour common stock. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Anyrepresentation to the contrary is a criminal offense. B. Riley Securities The date of this prospectus supplement is October 17, 2025. TABLE OF CONTENTS PageABOUT THIS PROSPECTUS SUPPLEMENTS-1CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSS-2PROSPECTUS SUPPLEMENT SUMMARYS-4THE OFFERINGS-5RISK FACTORSS-6USE OF PROCEEDSS-8DILUTIONS-9DIVIDEND POLICYS-10PLAN OF DISTRIBUTIONS-11LEGAL MATTERSS-12EXPERTSS-12WHERE YOU CAN FIND MORE INFORMATIONS-12INCORPORATION OF CERTAIN INFORMATION BY REFERENCES-12About This Prospectus1Where You Can Find More Information2Incorporation of Documents by Reference2Cautionary Note Regarding Forward-Looking Statements3Risk Factors4Use of Proceeds7Description of Debt Securities8Description of Capital Stock15Description of Preferred Stock18Description of Warrants23Description of Rights25Description of Units26Plan of Distribution29Legal Matters31Experts31 ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts and is part of an automatic registration statement on Form S-3 that we filed with the Securities andExchange Commission (the “SEC”), using a “shelf” registration process as a “well-known seasoned issuer” as defined in Rule 405under the Securities Act. The first part is this prospectus supplement, which describes the specific terms of this common stock offeringand also adds to and updates information contained in the accompanying prospectus and the documents incorporated by referenceherein. The second part, the accompanying prospectus dated October 16, 2025, provides more general information. Generally, whenwe refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between theinformation contained in this prospectus supplement and the information contained in the accompanying prospectus or any documentincorporated by reference herein or therein filed prior to the date of this prospectus supplement, you should rely on the information inthis prospectus supplement; provided that if any statement in one of these documents is inconsistent with a statement in anotherdocument having a later date for example, a document incorporated by reference in the accompanying prospectus, the statement in thedocument havi