There's Still Some Resistance to Reports of Extra‐High $Tc$ Superconductors

Ever since the copper oxide superconductors were first discovered seven years ago, any number of experimenters have come across a sample or two that have exhibited traits suggesting superconductivity at temperatures over 200 K. Typically the behavior was fleeting or elusive, disappearing after the material was taken through several thermal cycles or stubbornly refusing to show up in other samples produced in the same way. In most cases the sample consisted of several phases, and the experimenters could not link the high‐$Tc$ behavior to a particular phase. Robert Dynes of the University of California, San Diego, refers to these teasers as “leprechauns.” Paul Chu of the University of Houston has described them as “unidentified superconducting objects.”