  Contacts between high critical field superconductors and semiconductor
nanowires are important in the context of topological quantum circuits in which
superconductivity must be sustained to high magnetic fields. Here we
demonstrate gate-tunable supercurrent in NbTiN-Ge/Si core/shell nanowire-NbTiN
junctions. We observe supercurrents up to magnetic fields of 800 mT. The
induced soft superconducting gap measured by co-tunneling through a quantum dot
is 220 {\mu}eV. To improve contact transparency, we deposit an aluminum
interlayer prior to NbTiN and observe a systematic change in the device
pinch-off voltages with aluminum thickness. We inform future multi-step device
fabrication by observing that aluminum anneals with the Ge/Si nanowire at
180{\deg} celsius, the baking temperature of common electron beam lithography
resists.
