  We experimentally and theoretically investigate the influence of the magnetic
component of an electromagnetic field on high-order above-threshold ionization
of xenon atoms driven by ultrashort femtosecond laser pulses. The nondipole
shift of the electron momentum distribution along the light-propagation
direction for high energy electrons beyond the classical cutoff is found to be
vastly different from that below the cutoff. A V-shape structure in the
momentum dependence of the nondipole shift above the cutoff is identified for
the first time. With the help of classical and quantum-orbit analysis, we show
that large-angle rescattering of the electrons strongly alters the partitioning
of the photon momentum between electron and ion. The sensitivity of the
observed nondipole shift to the electronic structure of the target atom is
confirmed by three-dimensional time-dependent Schr\"odinger equation
simulations for different model potentials.
