We grew single crystals of non-centrosymmetric compounds CeTSi 3 and CeTGe 3 (T: transition metal), and studied the magnetic properties by measuring the electrical resistivity, magnetic susceptibility and magnetization. We also studied the effect of pressure on the electronic states in antiferromagnets CeTGe 3 (T: Co, Rh, Ir) by measuring the resistivity under pressure. No noticeable change of the Néel temperature was observed up to 8 GPa in CeRhGe 3 and CeIrGe 3 , which are far from the magnetic quantum critical point. On the other hand, the Néel temperature in CeCoGe 3 was strongly decreased as a function of pressure, and pressure-induced superconductivity was observed in the pressure region from 5.4 GPa to about 7.5 GPa. The slope of upper critical field H c2 at 6.5 GPa is found to be extremely large, with an upturn curvature of H c2 with decreasing temperature: ÀdH c2 =dT ¼ 200 kOe/K at the superconducting transition temperature T sc ¼ 0:69 K, revealing unconventional superconductivity.

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We present a detailed study of the high pressure phase diagram of the non-centrosymmetric antiferromagnet CeCoGe 3 by measurements of the ac calorimetry in a diamond anvil pressure cell. Under high pressure the magnetic ordering temperature shows a step like decrease due to various successive magnetic phases under high pressure. The magnetic order disappears at a critical pressure of p c % 5:5 GPa. Around the critical pressure bulk superconductivity has been detected in the ac calorimetric measurement.

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We succeeded in observing the de Haas-van Alphen (dHvA) effect in LaRuPO, which is a sister compound of iron-based oxypnictide superconductors. All the detected dHvA frequencies, which correspond to the maximum or minimum cross-sectional areas of Fermi surfaces, approximately follow the 1= cos dependence, where is a field-tilted angle from the tetragonal [001] direction to the [100] and [110] directions. The Fermi surfaces are found to consist of two cylindrical hole Fermi surfaces and two cylindrical electron Fermi surfaces on the basis of the similar cylindrical Fermi surfaces in LaFePO and the result of energy band calculations. The cyclotron effective mass in LaRuPO is light, ranging from 0.55 to 0.86 m 0 , which is compared with a large cyclotron mass in LaFePO. These two-dimensional Fermi surfaces in LaRuPO and LaFePO are also compared with the three-dimensional Fermi surfaces in LaFe 2 P 2 .

Superconductivity in the non-centrosymmetric crystal structure has been attracting a considerable interest since Bauer et al. reported superconductivity in CePt 3 Si which lacks inversion symmetry in the tetragonal crystal structure. 1) Recently the pressure-induced superconductivity was observed in some uranium-and cerium-based compounds with non-centrosymmetric crystal structures. 2-4) Many unconventional superconducting properties were found in these heavy fermion superconductors. It is, however, still unclear how the strong antisymmetric spin-orbit interaction (ASOI) due to the lack of inversion symmetry in the crystal affects on superconductivity. In order to elucidate the intrinsic effect of the strong ASOI on superconductivity, it is desirable to develop new non-centrosymmetric superconductors with weakly correlated electrons.Very recently, Oikawa et al. reported new ternary silicide superconductors ATSi 3 (A: Ca, Sr and Ba, and T: transition metal) with the BaNiSn 3 -type tetragonal crystal structure. 5) For example, polycrystalline CaPtSi 3 was found to show superconductivity below 2.