Observation of a Charge-Density Wave in α -U at Low Temperature

The discovery of a charge-density wave (CDW) in α-U at {~}43 K is reported. The mode corresponds to the condensation of a longitudinal-optic phonon near →q=[1/2, 0, 0] in which the atoms are displaced by {~}0.006 {}A from their special positions. Large precursor effects are seen in the phonon spectra. The wave vector of the CDW is related to that of the fundamental lattice in a rather complex way, which is discussed in terms of discommensurations between the CDW (α^' phase) and the primary α phase.