Symmetry breaking and restoring under high pressure: the amazing   behaviour of the "simple" alkali metals
  We argue that an ionic lattice surrounded by a Fermi liquid changes phase several times under pressure, oscillating between the symmetric phase and a low-symmetry dimerized structure, as a consequence of Friedel oscillations in the pair potential. Phase oscillations explain the tendency towards dimerization which has been recently reported for the light alkali metals under high pressure. Moreover, a restoring of the symmetric phase is predicted for such elements at an even higher density. 
G. G. N. Angilella, F. Siringo, R. Pucci