f-Electron Localized/Itinerant Crossover in ACoGa5 (A = U, Np, Pu, Am)

Measurements of magnetic susceptibility, specific heat, and electrical resistivity have been performed on the ACoGa 5 (A = U, Np, Pu, Am) series. The electrical resistivity of UCoGa 5 and PuCoGa 5 can be scaled upon the ρ( T ) data of the heavy-fermion superconductor CeCoIn 5 indicating a single spin fluctuation energy scale dominates the transport properties. The physical properties of the ACoGa 5 materials suggest the PuCoGa 5 superconductor resides near an itinerant/localized crossover of the 5 f electrons and is remarkably similar to the one that occurs in the light actinide elements.