Features of the thermopower of Mo–Re and Mo–Re–Nb alloys and the electronic–topological transition in these systems

The anomalous behavior of the thermopower of Mo1−xRex and Mo1−x−yRexNby alloys is investigated over a wide range of temperatures and concentrations (within the limits of the solid solution). An extremum on the concentration dependence of the thermopower at 10 K, observed for both of these systems at the same electron concentration ≈6.1 electrons/atom, attests to the presence of a critical energy Ec in the electronic spectrum of Mo at which an electronic–topological transition occurs in Mo under the influence of impurities. According to the theoretical ideas about the electronic spectrum of Mo, the closest Ec>EF0 corresponds to the bottom of the band, upon the crossing of which a new electron sheet of the Fermi surface appears. In the binary systems the Re impurity causes a new sheet of the Fermi surface to appear, and in the ternary systems it disappears as the Nb impurity is added. A quantitative comparison of the theory with experiment makes it possible to determine the gap Ec−Ef0 for Mo, which is found...