We report here our discovery of bulk superconductivity at rather high T, in samples having nominal compositions YNi4BCo, z (T, -12.5 K) and YNi&BsCo, z (T, 13.5 K). While YNi4BCo. '2 seems to be a single phase material, YNi2BSCp, q is a multiphase system, Our experimental results show that the two materials are distinct superconductors. Discovery of superconductivity in these materials is of significance since not only is their T, high (& 10 K) but they also have nickel in large proportions. No nickel-based ternary superconductor was previously known. PACS numbers: 74.10.+v, 74.25. Fy, 74.60.w, 74.70.AdWe have been studying the magnetic properties of sev-

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