Abstract: The invention relates to a powder of an alloy comprising uranium and molybdenum in ?-metastable phase, a composition of powders comprising this powder, and the uses of said alloy powder and of said composition of powders. The alloy powder comprising uranium and molybdenum in ?-metastable phase according to the invention is formed of particles comprising a nucleus which consists of said alloy, and which is covered with a layer of alumina positioned in contact with this nucleus. Applications: manufacture of nuclear fuel elements and, in particular, of fuel elements for experimental nuclear reactors; manufacture of targets intended for production of radioelements, which are useful in particular for medical imaging, such as technetium 99m.