  Resonant x-ray emission spectroscopy (RXES) was used to determine the
pressure dependence of the f-electron occupancy in the Kondo insulator SmB6.
Applied pressure reduces the f-occupancy, but surprisingly, the material
maintains a significant divalent character up to a pressure of at least 35 GPa.
Thus, the closure of the resistive activation energy gap and onset of magnetic
order are not driven by stabilization of an integer valent state. Over the
entire pressure range, the material maintains a remarkably stable intermediate
valence that can in principle support a nontrivial band structure.
