Electrical resistivity and specific heat of SmS in its gold phase have been investigated. Above $P_{\Delta }=2\mathrm{GPa}$, the resistivity is characteristic of a metallic heavy fermion compound. Ac calorimetry points out a phase transition with the occurrence of a new ground state. Analyses of the resistivity and of the specific heat and comparison with a microscopic probe (${}^{149}\mathrm{Sm}$ nuclear forward scattering) allow us to identify the onset of antiferromagnetism. Discussion will be made on the interplay of gap closing $(P<P_{\Delta })$, long-range magnetism $(P>P_{\Delta })$, and valence state.

• Received 30 August 2004

DOI:https://doi.org/10.1103/PhysRevB.70.220406