The layered lithium borocarbide LiBC, isovalent with and structurally similar to the superconductor ${\mathrm{MgB}}_2$, is an insulator due to the modulation within the hexagonal layers (BC vs ${\mathrm{B}}_2$). We show that hole doping of LiBC results in Fermi surfaces of B-C $p\sigma$ character that couple very strongly to B-C bond stretching modes, precisely the features that lead to superconductivity at $T_c\simeq 40\mathrm{K}$ in ${\mathrm{MgB}}_2$. Comparison of ${\mathrm{Li}}_{0.5}\mathrm{BC}$ with ${\mathrm{MgB}}_2$ indicates the former to be a prime candidate for electron-phonon coupled superconductivity at substantially higher temperature than in ${\mathrm{MgB}}_2$.

• Received 6 November 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.127001