Superconductivity of bulk CaC6
  We have obtained bulk samples of the graphite intercalation compound, CaC6, 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 MC6, metal-graphite compounds, which has rhombohedral symmetry. We have clearly shown the occurrence of superconductivity in the bulk sample at 11.5K, using magnetization measurements. 
N. Emery, C. Herold, M. d Astuto, V. Garcia, Ch. Bellin, J.F. Mareche,   P. Lagrange and G. Loupias