Evidence of s-wave superconductivity in ternary intermetallic La sub(3)Pd sub(4)Si sub(4)

We measured the temperature dependence of the magnetic penetration depth of La sub(3)Pd sub(4)Si sub(4) down to 0.02 T sub(c). We observe a temperature-independent behaviour below 0.25 T sub(c), which is firm evidence for a nodeless superconducting gap in this material. The data display a very small anomaly around 1 K which we attribute to the possible presence of a superconducting impurity phase. The superfluid density is well described by a two-phase model, considering La sub(3)Pd sub(4)Si sub(4) and the impurity phase. The present analysis suggests that the superconducting energy gap of La sub(3)Pd sub(4)Si sub(4) is isotropic, as expected for conventional BCS superconductors.