Superconductivity at 22K and 10K in the quaternary borocarbides RPd₄BC_X(R = Y,Lu)

Abstract

Recently we reported superconductivity in Y-Ni-B-C system, the first known quaternary superconducting system. One of the superconducting materials reported by us had the nominal chemical composition YNi₄BC_0.2. We examine, in this paper, effect of replacing nickel by palladium which is an obvious and natural step for us since we believe that the d- electrons are carriers of superconductivity in these materials. Our samples with the nominal composition YPd₄BC_X(0.2 < x < 1) have a superconducting minority phase with transition onset temperature as high as 22 K. Some of the samples show another superconducting transition at ~10K, indicating one more superconducting phase in this system. We have also investigated LuPd₄BC_0.2, (Lu being the end member of the rare earth series) which also shows existence of a superconducting phase with T_c~10K.