Unidentified Superconducting Objects

The search for new superconductors has been going on for decades, because the potential promise of room temperature superconductors (with useful properties, like high critical fields, high critical currents, chemical stability, the ability to be integrated in some way into wires, ribbons, or tapes) is so enormous.  Littering the metaphorical laboratory floor are various claims over the years of "unidentified superconducting objects" - a term attributed to Paul Chu to describe one-off, irreproducible hints of 200-300 K superconductivity, often features in resistivity or magnetization that look like they could originate in some unknown impurity phase of an already complex material.  I was reminded of this by a paper that showed up on the arxiv last night.  Most likely this will fade away, but these things are always intriguing.  Extraordinary claims require extraordinary evidence, of course.