Electronic properties of single-crystalline Fe1.05Te and Fe1.03Se0.30Te0.70

We report on a comprehensive study of the transport, specific heat, magnetic susceptibility, and optical spectroscopy on single crystal of Fe1.05Te, which undergoes a first-order phase transition near 65 K. We show that its physical properties are considerably different from other parent compounds of FeAs-based systems, presumably attributed to the presence of excess Fe ions. The charge transport is rather incoherent above the transition, and no clear signature of the gap is observed below the transition temperature. Strong impurity scattering effect exists also in Se-doped superconducting sample Fe1.03Se0.30Te0.70, leading to a relatively low T-c but a rather high upper critical field.