LK-99 (from the Lee-Kim 1999 research),[2] also called PCPOSOS,[3] is a gray–black, polycrystalline compound, identified as a copper-doped lead‒oxyapatite. A team from Korea University led by Lee Sukbae (이석배) and Kim Ji-Hoon (김지훈) began studying this material as a potential superconductor starting in 1999.[4]: 1 In July 2023, they published preprints claiming that it acts as a room-temperature su