Pressure-induced orthorhombic distortion of UMn₂

We present new results of high pressure X-ray diffraction experiments on UMn₂, showing that the cubic Laves phase distorts at pressures above about 3 GPa at ambient temperature. The analysis of the associated splitting of the diffraction lines reveals that this distortion is orthorhombic and qualitatively the same as the already known distortion observed at low temperatures. In contrast to earlier reported data, the volume compression curve shows a normal behaviour up to the highest pressure attained, about 30 GPa.