The temperature dependence of the resistivity of the bulk samples (disks with thickness of ~1 mm and diameter of ~5 mm) was measured in the temperature range of 50-300 K using the four-probe DC van der Pauw method . Four electrical contacts made of 0.05-mm diameter indium-tinned copper wire were soldered at equal distances to the cylindrical surfaces of the disks using (In + 1% Au + 4% Ag) alloy. The sample temperature was measured with a Cu(Fe)-Cu thermocouple and controlled by a standard temperature control device.