“…Although most of the optical experimental observation conducted by Bost et al [48] and other authors [1,[49][50][51][52] showed that -FeSi 2 is a direct band gap semiconductor with E g = 0.85-0.87 eV the papers related to band structure calculated by several authors [1,6,7,31,32] showed that it is both direct band gap semiconductor at Y and point as well as indirect band gap semiconductor along to Y along high symmetry directions. According to Filonov et al [1] and Eisebitt et al [34] the most important feature of the band structure is characterized by a direct band gap at point lies in between and Z k points which is 0.742 eV and 0.78 eV, respectively, whereas according to Christensen et al [32] and Eppenga et al [31] the calculated direct gap value at is about 0.80 eV and 0.92 eV, respectively.…”