An anonymous reader quotes a report from Ars Technica:

On Monday, the journal Nature released a report from Nanjing University researchers that had attempted to replicate an earlier paper that described a compound that superconducted at room temperature and relatively moderate pressures. Despite persuasive evidence that they’ve produced the same chemical, the team indicates they see no sign of superconductivity, even down to extremely low temperatures. The failure will undoubtedly raise further questions about the original research, which came from a lab that had an earlier paper on superconductivity retracted.

In 2020, the lab run by Ranga Dias at the University of Rochester reported a carbon-hydrogen-sulfur compound formed at extreme pressures could superconduct at room temperature. But the results were controversial, partly because it wasn’t clear that the paper included enough information for anyone else to produce the same conditions and because Dias was uncooperative when asked to share experiment data. Eventually, it became apparent that the team had used undocumented methods of obtaining some of the data underlying the paper, and it was retracted. But Dias continued to claim that the superconductivity was present. (There’s a good overview of the controversy on the American Physical Society website.)

Despite Nature retracting one of Dias’ papers, the journal published another paper on superconductivity from his group. In this case, a lutetium-hydrogen chemical doped with nitrogen was reported to superconduct at room temperature but at much lower pressures, which could allow it to be tested with somewhat less specialized equipment. Given the history, the claim was greeted with an even higher degree of skepticism than the earlier paper.