Specific-heat study on the noncentrosymmetric heavy-fermion superconductor CePt3Si

Specific-heat measurements were performed on a high-quality single crystal of CePt3Si without inversion symmetry in the tetragonal crystal structure. We observed distinct peaks in the specific-heat C at the superconducting transition temperature T-c = 0.46 K and the antiferromagnetic ordering temperature T-N = 2.25 K, compared to the previous data, indicating an improvement of the sample quality. The temperature dependence of the electronic specific-heat coefficient C-e/T below about 0.3 K is well described by the equation of C-e/T = gamma(s) + beta T-s with gamma(s) = 34.1 mJ/K-2.Mol and beta(s) = 1290 mJ/K-3.mol, evidencing the existence of line nodes in the superconducting energy gap. Furthermore, the electronic specific-heat coefficient gamma(s) in the superconducting state indicates a nonlinear magnetic field dependence gamma(s)(H) proportional to root H, which also supports the presence of line nodes.