Unconventional superconductivity in CeCoIn5 studied by the specific heat and magnetization measurements

We measured the low-temperature specific heat in magnetic fields up to 80 k Oe. together with the magnetization for the heavy-fermion superconductor Ce CoIn5 with the transition temperature T-c = 2.25 K. CeCoIn5, is a strong-co upling superconductor with a large jump in the specific heat, DeltaC/C-n(T- c) = 4.7. The heavy-fermion state is significantly formed below 1 K, reachi ng at least 1070 mJ/K-2.mol in magnetic fields. This large electronic speci fic heat coefficient at 0.25 K is. however, reduced with increasing magneti c field, ranging from 1070 mJ/K-2.mol at 50 kOe to 820 mJ/K-2.mol at 80 kOe , The upper critical field H-c2 at 0 K is estimated to be 116 kOe for H // [100] and 49.5 kOe for H // [001]. The present anisotropy of H-c2 is well e xplained by the anisotropic effective mass. but the magnitude of H-c2 is re duced strongly by the paramagnetic effect for both field directions.