15th International Conference on Muon Spin Rotation, Relaxation and Resonance

Superconductivity with a critical temperature $T_C$ $\sim$ 5.25 K was recently reported in the Cr-based superconductor Pr$_3$Cr$_{10-x}$N$_{11}$. The large upper critical field $H_{C2}$ $\sim$ 20 T, and the strong correlation between 3$d$ electrons derived from specific heat, suggest the unconventional superconductivity nature of this compound. We performed muon-spin rotation/relaxation ($\mu$SR) measurements on a high-quality polycrystalline of Pr$_3$Cr$_{10-x}$N$_{11}$ down to 0.027 K, and specific heat measurements under different magnetic fields up to 9 Tesla. Our $\mu$SR data indicate that time-reversal symmetry is broken in the superconducting state of Pr$_3$Cr$_{10-x}$N$_{11}$, and the superconducting energy gap is consistent with a $p$-wave model, which is also supported by the specific heat data.