Superconductivity in CaBi2

Superconductivity is observed with critical temperature T-c = 2.0 K in self-flux-grown single crystals of CaBi2. This material adopts the ZrSi2 structure type with lattice parameters a = 4.696(1) angstrom, b = 17.081(2) angstrom and c = 4.611(1) angstrom. The crystals of CaBi2 were studied by means of magnetic susceptibility, specific heat and electrical resistivity measurements. The heat capacity jump at T-c is Delta C/gamma T-c = 1.41, confirming bulk superconductivity; the Sommerfeld coefficient gamma = 4.1 mJ mol(-1) K-2 and the Debye temperature Theta(D) = 157 K. The electron-phonon coupling strength is lambda(el-ph) = 0.59, and the thermodynamic critical field H-c is low, between 111 and 124 Oe CaBi2 is a moderate coupling type-I superconductor. Results of electronic structure calculations are reported and charge densities, electronic bands, densities of states and Fermi surfaces are discussed, focusing on the effects of spin-orbit coupling and electronic property anisotropy. We find a mixed quasi-2D + 3D character in the electronic structure, which reflects the layered crystal structure of the material.