  We investigate the suppression of the visibility of Aharonov-Bohm
oscillations in a two-electron Mach-Zehnder interferometer that leaves the
single-electron current unchanged. In the case when the sources emit either
spin-polarized or entangled electrons, partial distinguishability of electrons
(coming from two different sources) suppresses the visibility. Two-particle
entanglement may produce behavior similar to "dephasing" of two-particle
interferometry.
