Onset of superconductivity in the antiferromagnetically ordered state of single-crystal ${\mathrm{DyNi}}_2$${\mathrm{B}}_2$C

Temperature-dependent static magnetization, ac magnetic susceptibility, and electrical-resistivity measurements of single-crystal ${\mathrm{DyNi}}_2$${\mathrm{B}}_2$C reveal bulk superconductivity below ${\mathit{T}}_{\mathit{c}}$=(6.2±0.1) K. This ${\mathit{T}}_{\mathit{c}}$ is well below the Néel temperature ${\mathit{T}}_{\mathit{N}}$=10.3 K. ${\mathrm{DyNi}}_2$${\mathrm{B}}_2$C is the first R${\mathrm{Ni}}_2$${\mathrm{B}}_2$C compound with ${\mathit{T}}_{\mathit{c}}$<${\mathit{T}}_{\mathit{N}}$. The upper critical magnetic field ${\mathit{H}}_{\mathit{c}2}$(T) increases approximately linearly from zero at 6.2 K to ∼5 kG at 2 K.