Electronic structure of the TbMn$_{0.33}$Ge$_{2}$ compound: Band calculation and optical experiment

The results of the investigation of the electronic structure and optical properties of the TbMn$_{0.33}$Ge$_{2}$ compound have been presented. The spin-polarized calculations of the band spectrum have been performed within the framework of the local spin density approximation (LSDA) with a correction for strong correlations in the 4$f$ shell of the rare-earth ion (the LSDA + $U$ method). The optical constants have been measured using the ellipsometric method and a number of spectral and electronic characteristics of the compound under investigation have been determined over a wide range of wavelengths. The interband part of the experimental dependence of the optical conductivity has been interpreted using the results of the calculation of the electron density of states.