The Pr-rich end $0\le x\le 0.25$ of the alloy series ${\mathrm{Pr}}_{1-x}{\mathrm{Nd}}_x{\mathrm{Os}}_4{\mathrm{Sb}}_{12}$ has been studied using muon spin rotation and relaxation. The end compound ${\mathrm{PrOs}}_4{\mathrm{Sb}}_{12}$ is an unconventional heavy-fermion superconductor, which exhibits a spontaneous magnetic field associated with broken time-reversal symmetry (TRS) in the superconducting phase. No such field is observed in the Nd-doped alloys for $x\ge 0.05$, indicating that TRS has been restored. The superfluid density from the vortex-lattice field distribution is insensitive to Nd concentration for $x\lesssim 0.2$, indicating that TRS restoration does not have a strong effect on the superconducting state. No ${\mathrm{Nd}}^{3+}$ static magnetism, ordered or disordered, is found down to the lowest temperatures of measurement.

• Received 29 June 2022
• Revised 18 August 2022
• Accepted 22 August 2022

DOI:https://doi.org/10.1103/PhysRevB.106.144508