We report on the optical and charge transport properties of novel alkali metal chalcogenides, Cs2Hg6S7 and Cs2Cd3Te4, pertaining to their use in radiation detection. Optical absorption, photoconductivity, and gamma ray response measurements for undoped crystals were measured. The band gap energies of the Cs2Hg6S7 and Cs2Cd3Te4 compounds are 1.63 eV and 2.45 eV, respectively. The mobility-lifetime products for charge carriers are of the order of ~10-3 cm2/V for electrons and ~10-4 cm2/V for holes. Detectors fabricated from the ternary compound Cs2Hg6S7 shows well-resolved spectroscopic features at room temperature in response to ϒ -rays at 122 keV from a
Co source, indicating its potential as a radiation detector.