Abstract. The anomalous linear term Δρ/ρ₀(B) and the positive normal component Δρ/ρ₀(B²) of magnetoresistance (MR) were calculated from B-MR dependence at T = 125 K for n-type lead sulphide with carrier concentration of 1.69×10¹⁹ cm^-3. Also the Fermi energy level E_F and Fermi integral F_1/2(η) were calculated in the temperature range of 4.2 - 300 K. It was found that the anomalous effects of the two contributions of MR were exhibited at the two opposite ditections of both current (I) and magnetic field (B). The magnitude of the constancy E_F is considered less than the usual known value in this temperature range. The anomalous MR may be attributed to the asymmetry relations among the induced Hall field at the two reversal directions of both B and I, and the anomalous behaviours of the other physical quantities may be due to the appearance of potent!al gradient as a result of deviation of the current vector from the axis of symmetry.

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