Superconductivity in actinides was first observed in thorium metal in 1929 [7], then in elemental uranium in 1942 [8], and in uranium compounds in 1958 [9]. A new class of uranium superconductors emerged in the 1980's with the discovery of uranium heavy fermion superconductors [10]. Further surprises came at the beginning of the century with the discovery of ferromagnetic superconductors in uranium systems [11] and the first observation of superconductivity in plutonium [12] and neptunium [13] compounds. The actinides (or actinoids) are located at the end of the periodic table (N=89 (Ac) or 90 (Th) to 103 (Lr)). Transuranium elements (or transuranics) are the chemical elements with atomic number (Z) greater than 92 (uranium) and due to their short half-life on a geological timescale, they are essentially synthetic elements. Above Z=103 (Lr), one talks about transactinides (or superactinides) elements. These latter elements have extremely short half-lives and no macroscopic quantity is available for the study of condensed-matter properties.
