  We report a study of the temperature dependence of the surface resistance RS
in the graphite intercalated compound (GIC) CaC6, where superconductivity at
11.5 K was recently discovered. Experiments are carried out using a copper
dielectrically loaded cavity operating at 7 GHz in a "hot finger"
configuration. Bulk CaC6 samples have been synthesized from highly oriented
pyrolytic graphite. Microwave data allows to extract unique information on the
quasiparticle density and on the nature of pairing in superconductors. The
analysis of RS(T) confirms our recent experimental findings that CaC6 behaves
as a weakly-coupled, fully gapped, superconductor.
