Electrical and thermal transport properties of RECu4 Au compounds, RE=Nd, Gd

We report the electrical and thermal transport properties of NdCu4 Au and GdCu4 Au compounds, crystallizing in the cubic MgCu4 Sn - type crystal structure, with space group F4 3m (no. 216).These properties are reported through measurements of electrical resistivity, ρ(T), thermoelectric power, S(T) and thermal conductivity, λ(T). ρ(T) and S(T) data indicate an antiferromagnetic (AFM)-like anomaly associated with a Néel temperature T_N=3.9 K and 10.9 K for NdCu4_{Au and GdCu4}Au compounds, respectively. ρ(T) data for both compounds shows a sudden drop at T_N. Above T_N, ρ(T) results are characteristic of an electron-phonon interaction in the presence of s-d scattering. Application of magnetic field slightly suppresses T_N value in GdCu4 Au compound from T_N=10.9 K in a field of 0 T to 10.1 K in a field of 6 T. S(T) data at low temperatures for both compounds shows a minimum at T_N. Critical analysis of S(T) in terms of the phenomenological resonance model yield the positions (E_f) and bandwidths (W_f) of the 4f band in both compounds: E_f=3.81(6)K, W_f=329(58) K for the Nd compound and E_f=18.2(4) K, W_f=306(5) K for the Gd compound. λ(T) for both compounds decreases linearly upon cooling from room temperature. The reduced Lorentz number L/_L0 deviates from the Wiedmann-Franz at low temperature with a strong increase in L/_L0 upon cooling the samples from room temperature.