Low field magnetic response of the non-centrosymmetric superconductor YPtBi

•We study the magnetic response of the non-centrosymmetric superconductor YPtBi.•DC and ac magnetization demonstrate YPtBi is a bulk superconductor.•We have determined the lower critical field by ac susceptibility.•We have determined the London penetration depth by muon spin rotation.•μSRμSR gives an upper bound on the internal field due to a mixed parity state.

The low-field magnetic response of the non-centrosymmetric superconductor YPtBi (Tc=0.77K) is investigated. Ac-susceptibility and dc-magnetization measurements provide solid evidence for bulk superconductivity with a volume fraction of ~70%. The lower critical field is surprisingly small: Bc1=0.008mT (T→0T→0). Muon spin rotation experiments in a transverse magnetic field of 0.01 T show a weak increase of the Gaussian damping rate σTFσTF below Tc, which yields a London penetration depth λ=1.6±0.2μm. The zero-field Kubo–Toyabe relaxation rate σKTσKT equals 0.129±0.004μs−1 and does not show a significant change below Tc. This puts an upper bound of 0.04 mT on the spontaneous magnetic field associated with a possible odd-parity component in the superconducting order parameter.