Specific Heat of the Ca-Intercalated Graphite Superconductor CaC$_6$
  The superconducting state of Ca-intercalated graphite CaC6 has been investigated by specific heat measurements. The characteristic anomaly at the superconducting transition (Tc = 11.4 K) indicates clearly the bulk nature of the superconductivity. The temperature and magnetic field dependence of the electronic specific heat are consistent with a fully-gapped superconducting order parameter. The estimated electron-phonon coupling constant is lambda = 0.60 - 0.74 suggesting that the relatively high Tc of CaC6 can be explained within the weak-coupling BCS approach. 
J. S. Kim (1), R. K. Kremer (1), L. Boeri (1), and F. S. Razavi (2)   ((1) Max-Planck-Institut fuer Festkoerperforschung, St...