title: Low-temperature specific heat of the heavy-fermion superconductor PrOs4Sb12.
abstract: We report the magnetic field dependence of the specific-heat C of single crystals of the first Pr-based heavy-fermion superconductor Pr(Os4Sb12. The variation of C at low temperature and the magnetic phase diagram inferred from C, the resistivity and magnetization provide compelling evidence of a doublet ground state. Two distinct superconducting anomalies in C indicate an unconventional superconducting state, where the splitting may arise from a weak lifting of the ground state degeneracy. In combination this identifies Pr(Os4Sb12 as a strong contender for quadrupolar pairing, i.e., superconductivity that is neither electron-phonon nor magnetically mediated.
authors.affiliation: Physikalisches Institut, Universität Karlsruhe, Wolfgang-Gaede-Strasse 1, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Vollmer
authors.forename: A
authors.initials: A
authors.lastname: Faisst
authors.forename: C
authors.initials: C
authors.lastname: Pfleiderer
authors.forename: H
authors.initials: H
authors.lastname: V  Löhneysen
authors.forename: E D
authors.initials: ED
authors.lastname: Bauer
authors.forename: P-C
authors.initials: PC
authors.lastname: Ho
authors.forename: V
authors.initials: V
authors.lastname: Zapf
authors.forename: M B
authors.initials: MB
authors.lastname: Maple