This thesis discusses research on the hot-electron transport in the spin-valve transistor (SVT). This 3-terminal device consists of a silicon emitter and collector with in between a base consisting of magnetic (NiFe and Co) and non-magnetic (Au) metal layers, a so-called spin-valve multilayer. Furthermore, the base includes thin layers of Pt and Au to form two different Schottky barriers with the Si emitter and collector. The collector current is dependent on the amount of current that is injected from the emitter into the Pt/NiFe/Au/Co/Au base, and on the magnetic state of the spin-valve multilayer. When the NiFe and Co layers are magnetized in the same direction (parallel), more collector current is measured, than when the layers are magnetized oppositely (anti-parallel). As described in this thesis, the spin-valve transistor can operate at room temperature and shows a large relative change in collector current (magnetocurrent > 300%) within small magnetic fields of only some Oe’s. Therefore, the spin-valve transistor is extremely suited to measure magnetic fields.