Editing Neptunium (section)

====Alloys====
Due to the presence of valence 5f electrons, neptunium and its alloys exhibit a very interesting magnetic behavior, like many other actinides. These can range from the itinerant band-like character characteristic of the [[transition metal]]s to the local moment behavior typical of [[scandium]], [[yttrium]], and the [[lanthanide]]s. This stems from 5f-orbital hybridization with the orbitals of the metal [[ligand]]s, and the fact that the 5f orbital is [[relativistic effects|relativistically]] destabilized and extends outwards.<ref name="Yoshida720">Yoshida et al., pp. 719–20.</ref> For example, pure neptunium is [[paramagnetic]], Np[[aluminium|Al]]<sub>3</sub> is [[ferromagnetic]], Np[[germanium|Ge]]<sub>3</sub> has no magnetic ordering, and Np[[tin|Sn]]<sub>3</sub> may be a [[heavy fermion material]].<ref name="Yoshida720" /> Investigations are underway regarding alloys of neptunium with uranium, [[americium]], [[plutonium]], [[zirconium]], and [[iron]], so as to recycle long-lived waste isotopes such as neptunium-237 into shorter-lived isotopes more useful as nuclear fuel.<ref name="Yoshida720" />

One neptunium-based [[superconductivity|superconductor]] alloy has been discovered with formula Np[[palladium|Pd]]<sub>5</sub>Al<sub>2</sub>. This occurrence in neptunium compounds is somewhat surprising because they often exhibit strong magnetism, which usually destroys superconductivity. The alloy has a tetragonal structure with a superconductivity transition temperature of −268.3&nbsp;°C (4.9&nbsp;K).<ref name="lanl" /><ref>{{cite journal |author=T. D. Matsuda |author2= Y. Hagal |author3= D. Aoki |author4= H. Sakai |author5= Y. Homma |author6= N. Tateiwa|author7=E. Yamamoto |author8=Y. Onuki |date=2009 |title=Transport properties of neptunium superconductor NpPd<sub>5</sub>Al<sub>2</sub> |journal=Journal of Physics: Conference Series |volume=150 |issue=4 | pages=042119 |doi=10.1088/1742-6596/150/4/042119|bibcode = 2009JPhCS.150d2119M |doi-access=free }}</ref>