Superconductivity at an elevated temperature in a new class of quaternary rare earth-transition metal boro-carbides

Our discovery of superconductivity at an elevated temperature (~12 K) in the system Y-Ni-B-C has opened up an entirely new area of research in superconductivity of intermetallics. We briefly present the results of our recent studies on magnetic history effects in YNi<SUB>2</SUB>B<SUB>2</SUB>C, the coexistence of superconductivity and magnetism in ErNi<SUB>2</SUB>B<SUB>2</SUB>C, the effect of substituents on superconductivity in YNi<SUB>2</SUB>B<SUB>2</SUB>C, the mixed valence of Ce in CeNi<SUB>2</SUB>B<SUB>2</SUB>C and superconductivity in Th-based borocarbides