The optical properties of the iron-chalcogenide superconductor K_(0.8)Fe_(2_v)Se_2 with a critical temperature Tc= 31 K have been measured over a wide frequency range in the ab planes above and below Tc.The conductivity is incoherent at room temperature but becomes coherent ( Drude-like) at T ≥ Tc.; however, R_□≈320 kΩ, wellabove the threshold for the superconductor-insulator transition at RD = h I4e26.91(0. Below T , the superfluid density ps0≈48 × 10~3 cm~(-2) places this material on the scaling line ps0/8≈4.4 б_(dc),Tc , but in a region associatedwith Josephson coupling, suggesting this material is inhomogeneous and constitutes a Josephson phase.
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