  We have performed polarized Raman scattering measurements on WTe$_2$, for
which an extremely large positive magnetoresistance has been reported recently.
We observe 5 A$_1$ phonon modes and 2 A$_2$ phonon modes out of 33 Raman active
modes, with frequencies in good accordance with first-principles calculations.
The angular dependence of the intensity of the peaks observed is consistent
with the Raman tensors of the $C_{2v}$ point group symmetry attributed to
WTe$_2$. Although the phonon spectra suggest neither strong electron-phonon nor
spin-phonon coupling, the intensity of the A$_1$ phonon mode at 160.6 cm$^{-1}$
shows an unconventional decrease with temperature decreasing, for which the
origin remains unclear.

Materials Science