Superconducting properties of iron-containing ternary silicides Lu-Fe-Si

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Superconductivity has been studied through electrical resistivity, Hall coefficient and AC susceptibility on a series of iron-containing rare earth silicides Lu-Fe-Si around the stoichiometric composition Lu_2Fe_3Si_5. The superconducting transition temperature T_c shows a maximum (-6.0K) on the stoichiometry and decreases with a deviation from itespecially on the Fe-rich side. The upper critical field for Lu_2Fe_3Si_5 increases linearly with decreasing temperature with a slope of about 1.5 Tesla/K, which is nearly the same as the ones for other off-stoichiometic samples in spite of the difference in T_2. All samples show a monotonic increase in resistivity with temperature in the range between T_c and 300K. The resistivity ratio <vho>(300K)/<rho>(6K) equals to -16 for Lu_2Fe_3Si_5 and decreases with a deviation from the stoichiometry especially on the Fe-rich side, which indicates the appearance of disorder in the sample as expected from the result of T_c. All samples show T^2 dependence of resistivity at lowtemperatures, which is interpreted in terms of electron-electron scattering. The carrier concentration of Lu_2Fe_3 obtained from Hall coefficiet is independent of temperature between T_c ad 300K, and is estimated to be 6 x 10^<27> m^<-3>, which is compared with 1 x 10^<27> m^<-3> for another isostructural sample Y_2Fe_3Si_5 with T_c = 2.4K. The difference in T_c between them would be ascribed to the difference of carrier concentration.