Superconductivity and role of pnictogen and Fe substitution in 112-LaPdxPn2(Pn=Sb,Bi)

We report on the epitaxial growth of As-free and phase-pure thin films of the 112-pnictide compounds LaPdxPn2 (Pn=Sb,Bi) grown on (100) MgO substrates by molecular beam epitaxy. X-ray diffraction, reflection high-energy electron diffraction, and x-ray photoelectron spectroscopy confirm the HfCuSi2 structure of the material with a peculiar pnictogen square net layer. The superconducting transition temperature Tc varies little with Pd concentration. LaPdxSb2 has a higher Tc (3.2 K) by about 20% compared with LaPdxBi2 (2.7 K). Fe substitution of Pd leads to a rapid decay of superconductivity, suggesting that these superconductors are conventional type II.