Temperature dependence of the band gap of AgIn$_{8}$S$_{12.5}$ single crystals

AgIn$_{8}$S$_{12.5}$ single crystals were grown by the vertical Bridgman method. The composition of the single crystals was determined by the X-ray spectral analysis method, and the crystal structure was determined by the X-ray diffraction method. It is shown that the grown single crystals crystallized in the cubic spinel structure. Transmittance spectra in the temperature range 10–320 K were used to determine the band gap of the crystals, which increased with decreasing the temperature.