RESISTIVITY AND SUPERCONDUCTIVITY OF AMERICIUM METAL UNDER PRESSURE UP TO 25-GPA

We report resistance data for americium metal under pressure up to 25 GPa and at temperatures down to 1.3 K. Samples of Am-243 with the doub le-hexagonal-closed-packed (d.h.c.p.) structure and also with the f.c. c. structure at ambient pressure were studied. The superconducting tra nsition temperature of americium is shown to increase in both cases co nsiderably with pressure, reaching a maximum value of 2.3 K at 6.6 GPa in the case of d.h.c.p. americium. The pressure variation of the supe rconducting critical temperature and the normal state properties of am ericium metal exhibit several anomalies, which are discussed with resp ect to phase transitions established by high pressure X-ray crystallog raphy.