Observation of zero resistivity in K-doped picene

We report the observation of zero resistivity (ρ) in a hydrocarbon superconductor, and describe the temperature dependence of ρ in metal-doped hydrocarbons. The resistivity of K-doped picene (K_xpicene) has been recorded from pellet samples in a four-terminal measurement mode. A drop in ρ is observed below 7 K for K_3.1picene and below 11 K for K _3.5picene, which clearly displays zero resistivity. The resistivity drop at 7 K is consistent with the superconducting critical temperature (T _c) obtained from the magnetic susceptibility of the 7 K phase of K₃picene, while the drop at 11 K is inconsistent with the T _c's of both the 7 and 18 K phases of K₃picene reported previously. The temperature dependence of ρ for both samples exhibits granular-metal-like behavior in the normal state.