Electrical resistance of the Mg 2 Ni and Mg 2 NiH 4 powders was measured under compressing up to 6 gigapascals (GPa), using the four-point probe method at 20°C. Effects induced by the high-pressure treatment and heating at 400°C with or without hydrogen source LiAlH 4 were also studied. The structure and hydrogenation properties of the samples recovered after quenching from high pressure and high temperature were investigated employing the techniques of X-ray diffraction and thermal analyses such as differential scanning calorimetry, thermogravimetry and differential thermal analysis. Decreased absorption/desorption temperatures were observed for the treated samples owing to the changes of microstructure and kinetic factor.