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EuGa 4 and EuAl 4 with the BaAl 4 -type tetragonal structure are Eu-divalent antiferromagnets with the Néel temperature T N = 16.5 K and 15.4 K, respectively. We clarified the Fermi surface properties from the results of de Haas-van Alphen experiments for EuGa 4 and EuAl 4 and energy band calculations of a non-4f reference compound SrGa 4 . Among two kinds of Fermi surfaces in EuGa 4 , there exists a cube-like electron Fermi surface with a vacant space in center, which most likely drives a charge density wave (CDW) via a nesting effect. This is realized in EuGa 4 under pressures, where the Fermi surface is expected to be modified so that the CDW transition is more easily induced. The similar CDW phenomenon is observed blow T CDW = 140 K in EuAl 4 at ambient pressure. Therefore, the cube-like Fermi surface below T CDW in EuAl 4 dose not exist at low temperatures because of the Fermi surface reconstruction, revealing only small ellipsoidal Fermi surfaces.

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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.

EuBi 3 with the AuCu 3 -type cubic structure is known to be a Eu-divalent antiferromagnet with the Néel temperature T N ' 7:5 K. We succeeded in growing a high-quality single crystal by the Bi self-flux method. The magnetization at 1.3 K for the magnetic field along the h100i direction increases linearly as a function of magnetic field, and saturates at a critical field H c ¼ 225 kOe, reaching a saturated magnetic moment of 7 B /Eu. H c is well explained by the magnetic exchange interaction based on a two-sublattice model, using the simple relation H c ¼ ðk B =3 B ÞðT N À p Þ, namely, H c ½kOe ¼ 4:9 ðT N À p Þ ½K, where p is the paramagnetic Curie temperature p ¼ À36 K. The present antiferromagnetic state is found to be stable under pressures up to 8 GPa, where the Néel temperature increases with increasing pressure, being T N ¼ 16:5 K at 8 GPa. From the results of de Haas-van Alphen experiments on EuBi 3 and energy band calculations for the non-4f reference compound SrBi 3 , the Fermi surface is found to consist of three types of nearly spherical Fermi surfaces.