1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
2. Department of Physics, University of Florida, Gainesville, Florida 32611, USA
3. European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, 76125 Karlsruhe, Germany

Correspondence to: J. L. Sarrao¹ Correspondence and requests for materials should be addressed to J.L.S. (e-mail: Email: sarrao@lanl.gov).

Abstract

Plutonium is a metal of both technological relevance and fundamental scientific interest. Nevertheless, the electronic structure of plutonium, which directly influences its metallurgical properties¹, is poorly understood. For example, plutonium's 5f electrons are poised on the border between localized and itinerant, and their theoretical treatment pushes the limits of current electronic structure calculations². Here we extend the range of complexity exhibited by plutonium with the discovery of superconductivity in PuCoGa₅. We argue that the observed superconductivity results directly from plutonium's anomalous electronic properties and as such serves as a bridge between two classes of spin-fluctuation-mediated superconductors: the known heavy-fermion superconductors and the high-T_c copper oxides. We suggest that the mechanism of superconductivity is unconventional; seen in that context, the fact that the transition temperature, T_c 18.5 K, is an order of magnitude greater than the maximum seen in the U- and Ce-based heavy-fermion systems may be natural. The large critical current displayed by PuCoGa₅, which comes from radiation-induced self damage that creates pinning centres, would be of technological importance for applied superconductivity if the hazardous material plutonium were not a constituent.