Americium under pressure

Electrical resistivity measurements of Americium metal under pressure in the normal and in the superconducting state are reported up to 27 GPa and down to temperatures of 0.4 K under magnetic field (<0.6 T). Resistivity under pressure indicates that superconducting transition temperature Tc rapidly increased with pressures in the 5 GPa range. The pressure dependence of the upper critical field is surprising, with μ0Hc(0) increasing rapidly with pressure (estimated to 1 T at the maximum of Tc). Contrary to expectations, the 5f electrons play probably an important role in this material even at low pressures. We do not observe any sign of an ordered state in this material, as judged by an anomaly in the resistivity, in contrast to the predictions, but possible weak “localisation” features deduced from normalised electrical resistivity curves.