Resistivity p(T) and absolute thermoelectric power S(Τ) have been measured for USb single crystaJs characterized by dicherent residual resistivity ratios, RRR = p(300 K)/p(4.2 K). A 50 μV/K peak of S(Τ) observed at 40 K for high RRR crystal vanishes for low RRR one. The p α Τ4 dependence observed below 40 K changes to the p α Τ5/2 one. These variations are ascribed to reduction of the magnoii drag echect by an increased incoherent magnetic scattering of carriers, possibly induced by a small change of composition. Resistivity anomaly is analysed above the antiferromagnetic transition temperature TN. We have found that resistivity decreases as t In t in the range 0.02 < t < 0.35, where t = (Τ -TN)/TN. It is ascribed to a semimetallic character of this compound.