Time-reversal symmetry-breaking superconductivity in heavy-fermion PrOs4Sb12 detected by muon-spin relaxation -: art. no. 067003

We report on muon-spin relaxation measurements of the 4f(2)-based heavy-fermion superconductor filled-skutterudite PrOs(4)Sb(12). The results reveal the spontaneous appearance of static internal magnetic fields below the superconducting transition temperature, providing unambiguous evidence for the breaking of time-reversal symmetry in the superconducting state. A discussion is made on which of the spin or orbital component of Cooper pairs carries a nonzero momentum.