Multiple-band Andreev transport in optimally doped superconducting oxypnictides

Using multiple Andreev reflections (MAR) effect spectroscopy of SnS junctions, we directly determine temperature dependences of the superconducting order parameters, excess Andreev current, and zero-bias conductance (ZBC) in polycrystalline samples of superconducting oxypnictides Sm$_{0.7}$Th$_{0.3O}$FeAs and NdO$_{0.6}$H$_{0.36}$FeA with almost optimal critical temperatures. It is shown that the results obtained are self-consistent and could be described in the framework of a two-band model. We estimate a dominating contribution 70–85% of the bands with the large gap to the total conductance.