United Microelectronics (UMC) shares experienced a pre-market plunge of 5.82% on Tuesday, marking a sharp reversal from recent gains.

The decline is primarily attributed to profit-taking activity after the company declined to confirm widespread market rumors regarding a potential collaboration with Intel. UMC had surged over 10% in the prior session on reports of a joint development deal for advanced process technologies. However, the company's official statement that it does not comment on speculative reports cast significant doubt on the partnership's certainty, prompting investors to lock in profits from the rapid run-up.

The selling pressure was further compounded by broader weakness across the semiconductor sector during the session, with several major chipmakers also trading lower, adding to the negative sentiment surrounding UMC's stock.