Superconductivity at 23 K in yttrium palladium boride carbide

Copper oxide compounds have dominated superconductivity research since 1986 because of their very high transition temperatures (T_cs). In contrast, no new families of high-T_c intermetallic compounds have been discovered since the A15-type Nb₃X compounds were first reported in 19531. The intermetallies with highest Jcs have all been based on niobium, with the highest T_cs being 20.7 K for bulk Nb₃Ga and 23.2 K for sputtered films of Nb₃Ge (refs 2, 3). Here we report the observation of superconductivity at 23 K in a multiple-phase bulk sample of a quaternary intermetallic, yttrium palladium boride carbide. This is higher than any T_c reported previously for a bulk intermetallic compound. Although the materials are not yet single-phase, the superconducting volume fraction is large. We propose that this compound may represent the first of a new family of superconducting intermetallics with relatively high T _cs.