The twofold decrease in hole concentration of all PbTe <NaTe> samples at 77–450 K and the same effect achieved at 77 K and heavy doping only due to introduction in PbTe of tin small addition, supplemented by observation in indicated range of temperature hysteresis in hole concentration, are the grounds for developing an other approach to a study of the energy spectrum in A(IV)B(VI) materials, an alternative two-band model. It is based on the common for these materials phenomenon — compensation of current carriers as a reaction on electroactive doping. The appearance of compensation is associated with initial (at temperatures below 77 K) two-charge process — participation in a single doping act of the pair of electrons due to their mutual attraction. With a rise in temperature, as with introduction of tin, the situation is changed. The study of all aspects of transformation is a task for further research.

In southern countries, including European states, solar collectors for additional water-heating systems are widely used. However, the disadvantage of such systems is that a considerable proportion of solar energy cannot be used with increasing water temperature and dissipates into the environment. It is proposed to use waste heat at a high temperature, which is supplied to a thermoelectric generator (TEG) operating on the basis of a temperature difference between the hot water in the solar collector and cold water supplied to a radiator on the other TEG side. This is a new application of thermoelectric converters, in which the converter can act not only as a source of electrical energy but also as a source of low-potential heat coming from the radiator. The total conversion efficiency in such devices can reach 90%. It is shown that the use of p -type legs in a TEG with the cleavage planes of the legs parallel to the heat-flux direction instead of the conventional parallel orientation results in an increase in the thermoelectric efficiency by 25% on average in the temperature range of 100–300°C.