Structure and superconductivity of the ternary intermetallics ofLa3Ni4Si4,La3Ni4Ge4,and La3Pd4Si4

Abstract

Ternary intermetallics of La3Ni4Si4, La3Ni4Ge4,and La3Pd4Si4 have been prepared by arc melting. These compounds take a body-centred latticewith an orthorhombic unit cell. The crystal structure of these compounds isU3Ni4Si4 type with thespace group Immm, consisting of the combination of structural units ofAlB2-type andBaAl4-type layers,as observed for La3Pd4Ge4. DC magnetization and electrical resistivity measurements indicate thatLa3Pd4Si4 is a type II superconductor with a critical temperature(Tc) of 2.15 K. Thelower critical field Hc1(0) is estimated to be 28 Oe. On the other hand, the upper critical fieldHc2(0) estimated by the WHH theory is 2.2 kOe. The coherence lengthξ(0) of 38 nm and thepenetration depth λ(0) of 376 nm are derived. The other compoundsLa3Ni4Si4 and La3Ni4Ge4 do not show superconductivity above 1.8 K.