Intragap states in SmB6

The results of wide-range measurements of the low-frequency, rf, and microwave conductivity in the typical mixed-valent narrow-gap semiconductor samarium hexaboride are presented. The established steplike anomaly of conductivity sigma(v) around 10 GHz is discussed in the framework of the exciton-polaron approach and coherent-state formation in SmB6 at helium temperatures. A combined analysis of the dc- and wide-range ac-transport characteristics and dielectric permittivity data at low temperatures is developed.