Stoichiometric intermetallic compounds were quenched from up to 1100C in order to produce thermal defects. The effect of this treatment upon the optical properties was investigated by using differential reflectometry techniques. The results were interpreted by attributing the optical absorption to the electronic structure. No additional localized states were found. A vacancy formation enthalpy of 1.04eV was obtained from the optical measurements, and an electron transfer of 0.5 electrons/vacancy was deduced by correlating optical measurements with the thermal defects and the so-called structural defects which were introduced by a change in composition. Influence of Thermal Defects on the Optical Properties of The Intermetallic Phases NiAl and FeAl. K.Schlemper, L.K.Thomas: Journal of Physics and Chemistry of Solids, 1994, 55[5], 421-6