  The heat capacity of superconducting Na(x)CoO(2)*yH(2)O was measured and the
data are discussed based on three different models: The thermodynamic
Ginzburg-Landau model, the BCS theory, and a model including the effects of
line nodes in the superconducting gap function. The electronic heat capacity is
separated from the lattice contribution in a thermodynamically consistent way
maintaining the entropy balance of superconducting and normal states at the
critical temperature. It is shown that for a fully gapped superconductor the
data can only be explained by a reduced (about 55 %) superconducting volume
fraction. The data are compatible with 100 % superconductivity in the case
where line nodes are present in the superconducting gap function.
