  Polarized Raman scattering measurements on IrTe$_2$ single crystals carried
out over 15~K - 640~K temperature range, and across the structural phase
transition, reveal new insights regarding the crystal symmetry.\ In the high
temperature regime three Raman active modes are observed at all studied
temperatures above the structural phase transition, rather than two as
predicted by the factor group analysis for the assumed $P\bar{3}m1$ symmetry.
This indicates that the actual symmetry of the high temperature phase is lower
than previously thought.\ Observation of an additional E$_g$ mode at high
temperature can be explained by doubling of the original trigonal unit cell
along the $c$-axis and within the $P\bar{3}c1$ symmetry.\ In the low
temperature regime (below 245 K) the new Raman modes appear as a consequence of
the symmetry lowering phase transition and corresponding increase of the
primitive cell.\ All the modes observed below the phase transition temperature
can be assigned within the monoclinic crystal symmetry.\ Temperature dependence
of the Raman active phonons in both phases are mainly driven by anharmonicity
effects. The results call for reconsideration of the crystallographic phases of
IrTe$_2$.
