Optical properties of FeGe$_{2}$ single crystal

The reflection spectra of FeGe$_{2}$ single crystal in a wide spectral region and in the temperature range from 80 to 310 K are studied. The energy of plasma oscillations, the relaxation frequency of charge carriers, and phonon frequencies are determined. Anisotropy of the optical properties is studied. It is shown that the phase transition from the collinear antiferromagnetic structure to the spiral one is accompanied by a significant rearrangement of electronic states.