Barium intra-atomic reconfiguration inBaC6

X-ray photoemission experiments on ${\mathrm{BaC}}_6$ show that Ba transfers only approximately one of its two conduction electrons to the graphite ${\pi }^{*}$ bands. However, the band occupied by the remaining conduction-electron charge differs significantly from the conduction band of Ba metal. Anomalous Ba core-electron binding-energy shifts show that this new band has substantial Ba $5d$ character, in agreement with bandstructure calculations.