Superconductivity in the ternary intermetallics ofLa3Ni4X4 (X = Si and Ge)

Abstract

Superconductivity in the ternary intermetallics ofLa3Ni4X4 (X = Si and Ge) with thecombination of AlB2 and BaAl4 layers is reported. Both compounds are type II superconductors with critical temperatures(Tc) of 1.0 and0.70 K for X = Si and Ge, respectively. The lower and the upper critical fields(Hc1(0) andHc2(0)) forX = Si are 107 Oe and 16.5 kOe,whereas those for X = Ge are 68 Oe and 2.6 kOe, respectively. The gradient−dHc2/dT ofLa3Ni4Si4 is extraordinarily higher than those of the other three analogues ofLa3Ni4Ge4 andLa3Pd4X4. The magneticpenetration depth (λ(0)) of 202 nm and Ginzburg–Landau coherence length(ξ(0)) of 14 nm are derivedfor X = Si, while they are206 and 36 nm for X = Ge.