The electrical resistivity ρ, the thermopower S and the magnetic susceptibility χ = M/B of the ternary compound EuNiGe 3 with the BaNiSn 3 -type structure have been measured at temperatures from 2 to 300 K. The measurements of ρ and S have been performed under pressures up to 1.8 GPa, together with ρ under pressures up to 8 GPa. With increasing temperature, the magnetic susceptibility χ shows a drastic increase, having a peak at the Néel temperature T N = 14 K and indicating the Curie-Weiss behavior at high temperature region. The effective magnetic moment of EuNiGe 3 is µ eff ≈ 7.7 µ B /Eu, indicating the 4f 7 (Eu 2+ ) electron configuration. The Néel temperature T N obtained from ρ(T ) and S (T ) curves increases linearly with increasing pressure. It is considered that the electron density of states of EuNiGe 3 in the vicinity of the Fermi energy has a small value and a weak energy dependence, and the Eu 2+ electronic configuration is stable.

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To clarify the Fermi surface properties based on the dimensionality of electronic states, we grew single crystals of V 2 Ga 5 , CoGa 3 , TiGa 3 , and ZrGa 3 (ZrAl 3 ) with different tetragonal structures and carried out de Haas-van Alphen experiments, together with full-potential linearized augmented plane wave band calculations. A nearly one-dimensional plate Fermi surface is obtained in the band calculations for V 2 Ga 5 with a flat tetragonal structure. The corresponding single crystal is of needle shape along the tetragonal [001] direction. The obtained Fermi surfaces of CoGa 3 are very similar to those of Ni 3 Ga with the AuCu 3 -type cubic structure because the crystal structure of CoGa 3 is nearly cubic and the corresponding single crystal is of pyramidal shape with a flat (111) plane. The Fermi surfaces of TiGa 3 are also very similar to those of YCu 2 Si 2 with the ThCr 2 Si 2 -type tetragonal structure. The cylindrical Fermi surfaces with concave and convex parts are realized in ZrGa 3 and ZrAl 3 with the flat Brillouin zone. The corresponding tetragonal structure is extremely long along the [001] direction. Fig. 1. (a) Three-, (b) two-, and (c) one-dimensional Fermi surfaces.

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