  We measure a transverse momentum kick in a Sagnac interferometer using
weak-value amplification with two postselections. The first postselection is
controlled by a polarization dependent phase mismatch between both paths of a
Sagnac interferometer and the second postselection is controlled by a polarizer
at the exit port. By monitoring the darkport of the interferometer, we study
the complementary amplification of the concatenated postselections, where the
polarization extinction ratio is greater than the contrast of the spatial
interference. In this case, we find an improvement in the amplification of the
signal of interest by introducing a second postselection to the system.
