Measurement for Transport and Thermal Properties of Materials with anomalous thermoelectric behaviors at Low Temperatures below 1K

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Aim for our research is as follows :1.Construction of the measurement systems for thermoelectric power S, thermal conductivity κ and the other physical quantities characterizing properties of solid from the room temperature down to 0.1K.2.Identification of materials with anomalous thermoelectric properties at low temperatures, and research for their nature via transport and thermal quantities such as electrical resistivity p and specific heat C.In the research term, we finished constructing the several systems including S and κ on a ^3He-^4He dilution frigerator, C under pressure using a ^3He-cryostat, and investigated the magnetic properties of several 4f-electron compounds from experimental results obtained using these systems. The main research results are as follows :1.We measured S and C of Ce(Ni,Pd)_2Ge_2 well below 1 K, and detected a quantitative close relation in between the Sommerfeld coefficient γ and the S/T reflecting a non-Fermi liquid nature in the lowest temperature range.2.Mitsuda et al. reported the pressure-induced ferromagnetic transition at 2 K with small magnetic moment in a valence transition compound (Yb_<0.8>Y_<0.2>)InCu_4 by magnetization measurement. We detected a sharp peak at 2 K in C under 1.2 GPa, and obtained about 20 % of the full moment of Yb^<3+> ion is frozen with this phase transition from the entropy consideration, concluding this transition is from a bulk property and intrinsic in this compound.3.We measured p and C of a valence fluctuator EuPd_2Si_2 and its 'isovolume' diluted alloys (Eu(La_<0.67>Y_<0.33>)Pd_2Si_2 between 2 and 300 K. We found both the resistance minimum at 20 K and the C/T upturn reaching large amount at low temperatures below 30 K for the alloys beyond 25 % of substitution of Eu by (La_<0.67>Y_<0.33>). We consider they may originate from the Kondo effect, and the measurements of S for these alloys are in progress.