Crystallogenesis /Luminescence /Radioluminescence /Commensurate-incommensurate phase transition /Absorption spectroscopy/ Emission spectroscopy/Tetravalent actinidesAbstract Some properties of thorium tetrabromide which have become apparent since 1975 are examined. Until the discovery of its radioluminescence, no particular attention was given to this halide, but subsequently research on this compound was intensified.Owing to the exceptional radioresistance of the material, studies concerning the possibilities of using ThBr 4 as a radiation detector, a target detector for nuclear reactions and a converter of nuclear energy into luminous energy have been given priority. Later, its use as a matrix for high resolution spectroscopy of M 4+ actinide ions (because of the properties of the Th 4+ ) ion was considered. The interpretation of the absorption and emission spectra required a complete characterization of vibrational and structural properties of ThBr 4 , especially at low temperature. It was only then discovered that ThBr 4 underwent a commensurate -incommensurate phase transition towards 90 Κ and that the modulated phase still existed at 4 K. Extensive research was begun which later expanded into numerous fields; some of these, such as phase transitions dynamics and the effect of the incommensurability on spectroscopic and thermodynamic properties are presently under study. Much of this work required the availability of large (several cm 3 ) single crystals of ThBr 4 and consequently production of this compound on the kilogram scale was carried out.