We discuss the type of pairing in the hexagonal pnictide superconductor SrPtAs, taking into account its multiband structure. The topological chiral d-wave state with time-reversal-symmetry breaking has been anticipated from the spontaneous magnetization observed by the muon-spinrelaxation experiment. We point out in this paper that the recent experimental reports on the nuclear-spin-lattice relaxation rate T −1 1 and superfluid density ns(T ), which seemingly support the conventional s-wave pairing, are also consistent with the chiral d-wave state. The compatibility of the gap and multiband structures is crucial in this argument. We propose that the measurement of the bulk quasiparticle density of states would be useful for the distinction between two pairing states.

The pairing symmetry of the hexagonal pnictide superconductor SrPtAs is discussed with taking into account its multiband structure. The topological chiral d-wave state with time-reversal-symmetry breaking has been anticipated from the spontaneous magnetization observed by the muon-spinrelaxation experiment. We point out in this paper that the recent experimental reports on the nuclearspin-lattice relaxation rate T −1 1 and superfluid density n s (T ), which seemingly support the conventional s-wave pairing, are also consistent with the chiral d-wave state. The compatibility of the gap and multiband structures is crucial in this argument. We propose that the measurement of the bulk quasiparticle density of states would be useful for the distinction between two pairing states.