Abstract
We have introduced defects into clean samples of the organic superconductor -BEDTTTF 2CuSCN2 in order to determine their effect on the temperature dependence of the interlayer conductivity and the critical temperature Tc. We find a violation of Matthiessen’s rule that can be explained by a model of involving a defect-assisted interlayer channel which acts in parallel with the bandlike conductivity. We observe an unusual dependence of Tc on residual resistivity, inconsistent with the generalized Abrikosov-Gor’kov theory for an order parameter with a single component, providing an important constraint on models of the superconductivity in this material.