Superconductivity of BulkCaC6

We have obtained bulk samples of the graphite intercalation compound, ${\mathrm{CaC}}_6$, by a novel method of synthesis from highly oriented pyrolytic graphite. The crystal structure has been completely determined showing that it is the only member of the ${\mathrm{MC}}_6$, metal-graphite compounds that has rhombohedral symmetry. We have clearly shown the occurrence of superconductivity in the bulk sample at 11.5 K, using magnetization measurements.