  We have fabricated and tested an atom chip that operates as a matter wave
interferometer. In this communication we describe the fabrication of the chip
by ion-beam milling of gold evaporated onto a silicon substrate. We present
data on the quality of the wires, on the current density that can be reached in
the wires and on the smoothness of the magnetic traps that are formed. We
demonstrate the operation of the interferometer, showing that we can coherently
split and recombine a Bose-Einstein condensate with good phase stability.
