Proposal of a new model for the modulated structure of α-uranium

Abstract The modulated structure of α-uranium is analysed in the framework of the theory of superspace groups. Arguments are given which lead to the (3 + 2) D superspace group Pmcm ( 1 2 βγ) as the most probable one. The consequences for the structure are derived. The most important one is, that there are two independent atoms in the unit-cell, one with a displacement along b and c and the other with a displacement only along a . This model is quite different from that previously found, which has only one independent atom, and a modulation in all three directions.