By Peter Weiss
A humble metallic powder made headlines last year when Japanese researchers found it to be a superconductor–a material in which electric current flows resistancefree (SN: 3/3/01, p. 134: Run-of-the-mill compound becomes superstar). Most remarkable–and inexplicable–was how warm the compound, magnesium diboride, could get before its superconductivity disappeared.
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Now, Hyoung Joon Choi and his colleagues at the University of California, Berkeley and Lawrence Berkeley (Calif.) National Laboratory explain the superconductor’s exceptionally high transition temperature of 39 kelvins, as well as other puzzling properties of the material. So-called conventional superconductors, of which magnesium diboride is a member, typically become superconductors below 20 kelvins.