  Gate-controlled supercurrent (GCS) in superconductor nanobridges has recently
attracted attention as a means to create superconducting field effect
transistors. Despite the clear advantage for applications with low power
consumption and high switching speeds, the microscopic mechanism of the field
effect is still under debate. In this work, we realize GCS for the first time
in an epitaxial superconductor, which is created as a shell on an InAs
nanowire. We show that the supercurrent in the epitaxial Al layer can be
switched to the normal state by applying $\simeq\pm$ 23$\,$V on a bottom gate
insulated from the nanowire by a crystalline hBN layer. Our extensive study on
the temperature and magnetic field dependencies of GCS suggests that hot
electron injection alone cannot explain our experimental findings.
