Superconductivity in diamond
Workers in Russia and Los Alamos, USA report in Nature1 superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2500-2800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond (carbon) is a bulk, type-II superconductor below the superconducting transition temperature Tc 4 K.
Boron has one less electron than carbon and, because of its small atomic radius, is relatively easily incorporated into diamond. The boron acts as a charge acceptor and the resulting diamond is effectively hole-doped.