La 2 Pd 2 In: superconductivity and lattice properties at ambient and elevated pressures.

Lattice and electronic properties of La 2 Pd 2 In were studied at ambient and elevated pressures so as to determine features related to a specific atomic coordination without any influence of magnetism. We describe temperature dependences of lattice parameters, heat capacity and electrical resistivity of single-crystalline La 2 Pd 2 In (s.g. P 4/ mbm ) in a broad temperature range 0.09-300 K. Together with the anisotropic effect of hydrostatic pressure, showing that the lattice is more compressible in the basal plane, we can conclude that the lattice is affected by degrees of freedom of the La atoms with positions not imposed by symmetry. The lattice anisotropy is smaller than that found for isostructural ferromagnet Ce 2 Pd 2 In. The equilibrium bulk modulus B 0 = (48 ± 3) GPa was determined on the basis of individual linear compressibilities. Measurement of electrical resistivity indicated a superconducting state below T = 0.59 K with a low critical field 0.005 T at T = 380 mK. The onset of superconducting state as a bulk property of La 2 Pd 2 In was confirmed by measurements of specific heat and AC magnetic susceptibility. Experimental data can be accounted by first-principles electronic-structure calculations based on density-functional theory. The measured Sommerfeld coefficient γ = 10.6 mJ mol -1  K -2 , only marginally exceeding the calculated γ = 9.34 mJ mol -1  K -2 , indicates only weak electronic correlations.