CONDUCTIVITY AND MAGNETORESISTANCE OF FESI IN THE ANDERSON-LOCALIZED REGIME

The temperature dependence of the conductivity, sigma(T), of FeSi at T approximate to 100-170 K follows the Arrhenius law with the value of the band gap E(g) approximate to 50 +/- 5 meV. Between T-nu approximat e to 15-25 K and T-g approximate to 3-4 K it agrees with the Mott-typ e varriable-range hopping. No tendency of saturation in sigma(T) is ob served down to 1.4 K. The relative magnetoresistance, Delta p/p, is ne gative at T less than or equal to 4.2 K and H < 1 T with the amplitude value approximate to 0.2%. In higher fields, up to 35 T, it is positi ve and demonstrates a complex magnetic field and temperature dependenc e suggesting both positive and negative contributions. At T greater th an or equal to 77 K, Delta rho/rho is negligible. The positive compone nt of Delta rho/rho agrees with that of the Osaka model which takes in to account both correlation and spin-flip effects. The negative contri bution is attributed to the Zeeman splitting of the mobility threshold predicted by Kamimura and Kurobe. The temperature dependence of the h opping frequency with the pre-exponent nu(0) approximate to 2.8 x 10(1 2) s(-1), the value of the internal field, H-1 approximate to 60 kOe, and the maximum value of the correlation energy, U-m approximate to 17 K, are obtained.