  The superconducting pyrochlore oxide Cd2Re2O7 (Tc = 1 K), which is now
considered as a candidate of the spin-orbit-coupled metal, shows an
inversion-symmetry-breaking structural transition at Ts1 = 200 K. Ts1 decreases
with increasing pressure and disappears at around Pc = 4:2GPa, where at least
four high-pressure phases with tiny structural distortions are suggested by
means of powder X-ray diffraction [Yamaura PRB 2017]. We have carried out Raman
scattering experiments to investigate changes in the crystal symmetry under
high pressures up to 4.8 GPa. A structural transition at 1.9-3.0 GPa and the
recovery of inversion symmetry above Pc are observed at 12 K.
