  We investigate electron momentum distributions from single ionization of Ar
by two orthogonally polarized laser pulses of different color. The two-color
scheme is used to experimentally control the interference between electron wave
packets released at different times within one laser cycle. This intracycle
interference pattern is typically hard to resolve in an experiment. With the
two-color control scheme these features become the dominant contribution to the
electron momentum distribution. Furthermore the second color can be used for
streaking of the otherwise interfering wave packets establishing a which-way
marker. Our investigation shows that the visibility of the interference fringes
depends on the degree of the which-way information determined by the
controllable phase between the two pulses.
