Bulk superconductivity at an elevated temperature (${\mathit{T}}_{\mathit{c}}$≊12 K) in a nickel containing alloy system Y-Ni-B-C

We report here our discovery of bulk superconductivity at rather high ${\mathit{T}}_{\mathit{c}}$ in samples having nominal compositions ${\mathrm{YNi}}_4$${\mathrm{BO}}_{0.2}$ (${\mathit{T}}_{\mathit{c}}$≊12.5 K) and ${\mathrm{YNi}}_2$${\mathrm{B}}_3$${\mathrm{O}}_{0.2}$ (${\mathit{T}}_{\mathit{c}}$≊13.5 K). While ${\mathrm{YNi}}_4$${\mathrm{BC}}_{0.2}$ seems to be a single phase material, ${\mathrm{YNi}}_2$${\mathrm{B}}_3$${\mathrm{C}}_{0.2}$ 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 ${\mathit{T}}_{\mathit{c}}$ high (>10 K) but they also have nickel in large proportions. No nickel-based ternary superconductor was previously known.