Electrical resistivity and specific heat studies of NpFe4Al8

Electrical resistivity and specific heat of a stoichiometric NpFe4Al8 polycrystalline sample were measured between 2 and 300 K, and under 0-9 T applied magnetic fields. Both measurements confirm the occurrence of magnetic ordering at 135(5) K. The electrical resistivity displays a second anomaly at 113(5) K, which was ascribed to the neptunium magnetic ordering. There is a clear evidence of predominant ferromagnetic-like interactions in this compound, but with a complex magnetic structure, as previously suggested by the magnetic measurements and theoretical calculations. The high γ = 183(10) mJ mol−1 K−2 value classifies the NpFe4Al8 compound as a moderate heavy fermion.