Low-temperature anomalies of the Hall coefficient in FeSi

The temperature dependence of the Hall coefficient in the interval 1.8-300 K is investigated in detail in high-quality single-crystal samples of a Kondo insulator - iron monosilicide. It is established that the parameter R-H(T,H = 12.5 kOe) changes sign twice in the temperature interval employed, and at temperatures below T-m approximate to 7 K an anomalous (magnetic) component appears in the angular and field dependences of the Hall voltage. The results of the experimental investigations of R-H(T, H-0) in FeSi are discussed on the basis of the phase diagram in the model of an excitonic insulator. (C) 1998 American Institute of Physics. [S0021-3640(98)01122-0].