  We study the propagation of cold-atom wave packets in an interferometer with
a Mach-Zehnder topology based on the dynamical phase of Bloch oscillation in a
weakly forced optical lattice with a narrow potential barrier that functions as
a cold-atom wave packet splitter. We calculate analytically the atomic wave
function, and show that the expected number of atoms in the two outputs of the
interferometer oscillates rapidly as a function of the angle between the
potential barrier and the forcing direction with period proportional to the
external potential difference across a lattice spacing divided by the lattice
band energy scale. The interferometer can be used as a high precision force
probe whose principle of operation is different from current interferometers
based on the overall position of Bloch oscillating wave packets.
