  Controlling electronic transport through a single-molecule junction is
crucial for molecular electronics or spintronics. In magnetic molecular
devices, the spin degree-of-freedom can be used to this end since the magnetic
properties of the magnetic ion centers fundamentally impact the transport
through the molecules. Here we demonstrate that the electron pathway in a
single-molecule device can be selected between two molecular orbitals by
varying a magnetic field, giving rise to a tunable anisotropic
magnetoresistance up to 93%. The unique tunability of the electron pathways is
due to the magnetic reorientation of the transition metal center, resulting in
a re-hybridization of molecular orbitals. We obtain the tunneling electron
pathways by Kondo effect, which manifests either as a peak or a dip line shape.
The energy changes of these spin-reorientations are remarkably low and less
than one millielectronvolt. The large tunable anisotropic magnetoresistance
could be used to control electronic transport in molecular spintronics.
