Magnetic properties, electronic structure and X-ray spectra of RCo9Si4 compounds (R=Y, Gd, Tb)

NpX3 (AuCu3-type structure) compounds with X=Al, Ga, Ge, In and Sn were studied up to 50 GPa using the energy dispersive X-ray diffraction (EDXRD) technique. No structural phase transitions were observed for any of the compounds studied up to the highest pressures attained. The compressibility was measured for each compound and compared with theory. The results for NpX3 are compared with those previously obtained for UX3.