Superconductivity in the quaternary compounds LNi4B4C with L=Y, Ho, Er, and Tm.

Abstract

We have discovered a superconducting phase of ${\mathrm{YNi}}_{4}$${\mathrm{B}}_{4}$C with a tetragonal-symmetric structure in arc-melted samples. The superconducting transition temperature (${\mathit{T}}_{\mathit{c}}$=15.9 K) of the ${\mathrm{YNi}}_{4}$${\mathrm{B}}_{4}$C phase is comparable to that of the ${\mathrm{YNi}}_{2}$${\mathrm{B}}_{2}$C phases reported by Cava et al. Superconductivity is found not only in ${\mathrm{YNi}}_{4}$${\mathrm{B}}_{4}$C, but also in L${\mathrm{Ni}}_{4}$${\mathrm{B}}_{4}$C, containing the magnetic rare-earth elements Ho, Er, and Tm. Their ${\mathit{T}}_{\mathit{c}}$ values are 6.3, 10.5, and 9.9 K, respectively.