Electron-energy bands in single-crystalline La-intercalated graphite

A graphite-intercalation compound (GIG) of La was prepared by a thermally induced surface reaction of a metallic La film on a graphite (0001) substrate. The LEED pattern shows a characteristic (root 3 x root 3) R30 degrees reconstruction pointing to the formation of LaC6. Angle-resolved photoemission combined with Fermi-surfaces mapping reveals a strongly anisotropic electronic bandstructure of La-GIC. The unfolded pi-symmetry graphite-derived bands in the La intercalation compound may be described in good approximation within a simple rigid-band model by charge transfer from La to graphite. Despite the presence of filled La-5d states large photoemission intensities close to the Fermi level around the K-points of the nonreconstructed Brillouin zone are related to carbon-derived p(pi*)-bands, which become partly occupied in the GIC.