Electronic structure of theBa4C60superconductor

We study the electronic structure of the superconducting body-centered-orthorhombic fulleride ${\mathrm{Ba}}_{4}{\mathrm{C}}_{60}$ using the local-density approximation in the density-functional theory. It is found that Ba states are strongly hybridized with ${\mathrm{C}}_{60}$ states through pentagons, explaining the observed lattice-constant differences, $agbgc.$ Due to this hybridization and to a rather low symmetry of the lattice causing the splitting of states, the ${t}_{1g}$-derived conduction band partially occupied by two electrons is found to be relatively wide. Fermi surfaces also show noncubic nature and contain dual quasiplanar sheets parallel to the $a\ensuremath{-}b$ plane in the momentum space, giving rise to a quasinesting vector parallel to the c axis.