Anomalous scattering of quasiparticles by Co and Cu impurities in the Kondo semimetal CeNiSn

We present results of the magnetic susceptibility chi(T), electrical resistivity rho(T) and Hall coefficient R-H(T) for CeNi1-xTxSn (T = Co and Cu, 0 less than or equal to x less than or equal to 0.05). Co impurities decrease chi along all the principal axes, whereas Cu impurities increase. Both impurities at x = 0.01 cause a remarkable increase in rho at 1.4 K with 970 mu Omega cm/at% Cu at maximum. For x = 0.05, rho(T) is saturated to a lower value than that for x = 0.01. R-H(T) for x = 0.01 Co and Cu becomes negative below about 4 K and the absolute value is smaller than that for x = 0, while R-H for x = 0.05 remains positive down to 1.6 K. The nonmonotonic dependence of rho(T) and R-H(T) on x indicates extremely strong scattering of quasiparticles from nonmagnetic impurities in the presence of pseudogap.