Valence instability across magnetostructural transition in USb${}_2$

We have performed pressure dependent X-ray diffraction and resonant X-ray emission spectroscopy experiments on USb${}_2$ to further characterize the AFM-FM transition occurring near 8 GPa. We have found the magnetic transition coincides with a tetragonal to orthorhombic transition resulting in a 17% volume collapse as well as a transient $\mathit{\text{f}}$-occupation enhancement. Compared to UAs${}_2$ and UAsS, USb${}_2$ shows a reduced bulk modulus and transition pressure and an increased volume collapse at the structural transition. Except for an enhancement across the transition region, the $\mathit{\text{f}}$-occupancy decreases steadily from 1.96 to 1.75.