title: Superconductivity on the border of weak itinerant ferromagnetism in UCoGe.
abstract: We report the coexistence of ferromagnetic order and superconductivity in UCoGe at ambient pressure. Magnetization measurements show that UCoGe is a weak ferromagnet with a Curie temperature T(C)=3 K and a small ordered moment m(0)=0.03 micro(B). Superconductivity is observed with a resistive transition temperature T(s)=0.8 K for the best sample. Thermal-expansion and specific-heat measurements provide solid evidence for bulk magnetism and superconductivity. The proximity to a ferromagnetic instability, the defect sensitivity of T(s), and the absence of Pauli limiting, suggest triplet superconductivity mediated by critical ferromagnetic fluctuations.
authors.affiliation: Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands.
authors.forename: N T
authors.initials: NT
authors.lastname: Huy
authors.forename: A
authors.initials: A
authors.lastname: Gasparini
authors.forename: D E
authors.initials: DE
authors.lastname: de Nijs
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
authors.forename: J C P
authors.initials: JC
authors.lastname: Klaasse
authors.forename: T
authors.initials: T
authors.lastname: Gortenmulder
authors.forename: A
authors.initials: A
authors.lastname: de Visser
authors.forename: A
authors.initials: A
authors.lastname: Hamann
authors.forename: T
authors.initials: T
authors.lastname: Görlach
authors.forename: H V
authors.initials: HV
authors.lastname: Löhneysen