In this letter, we describe the observation of the interference of conduction paths induced by two donors in a nanoscale silicon transistor, resulting in a Fano resonance. This demonstrates the coherent exchange of electrons between two donors. In addition, the phase difference between the two conduction paths can be tuned by means of a magnetic field, in full analogy to the Aharonov–Bohm effect. One of the crucial ingredients for donor based quantum computation is phase coherent manipulation of electrons. This has not been achieved as yet, and this work presents a stepping stone.