Evidence for two-gap superconductivity in the non-centrosymmetric compound LaNiC2

We study the superconducting properties of the non- centrosymmetric compound LaNiC2 by measuring the London penetration depth 1k(T), the specific heat C(T, B) and the electrical resistivity ( T, B). Both 1( T) and the electronic specific heat Ce(T) exhibit behavior at low temperatures that can be described in terms of a phenomenological two-gap Bardeen-Cooper-Schrieffer (BCS) model. The residual Sommerfeld coefficient in the superconducting state, 0(B), shows a rapid increase at low fields and then an eventual saturation with increasing magnetic field. A pronounced upturn curvature is observed in the upper critical field Bc2(T) near Tc. All these experimental observations support the existence of two-gap superconductivity in LaNiC2.