Thermoelectric properties of Ce(Ni, Pd)₂Ge₂ at low temperatures below 1 K

Thermoelectric power S of single crystals for a nonmagnetic heavy fermion compound CeNi₂Ge₂ and for the alloys of Ce(Ni_1-xPd_x)₂Ge₂ was investigated well below 1 K. S/T, S divided by temperature T, logarithmically increases with lowering temperature below 10 K, approaching a large magnitude of about 10 μV/K² in the lowest temperatures along the c-axis of a tetragonal crystal structure for the sample with x=0.06. This behavior strikingly coincides with the temperature dependence of C/T which leads to a large Sommerfeld coefficient γ of 630 mJ/K² mol in the zero-temperature limit. On the other hand, S/T for CeNi₂Ge₂ shows a complex temperature dependence at low temperatures in both axes, and is different from its C/T behavior. These results are regarded as the consequence originating from a non-Fermi-liquid nature evolved at low temperatures in the vicinity of the antiferromagnetic quantum critical point.