  We report resistance versus magnetic field measurements for a
La0.65Sr0.35MnO3/SrTiO3/La0.65Sr0.35MnO3 tunnel junction grown by
molecular-beam epitaxy, that show a large field window of extremely high
tunneling magnetoresistance (TMR) at low temperature. Scanning the in-plane
applied field orientation through 360^/circ, the TMR shows 4-fold symmetry,
i.e. biaxial anisotropy, aligned with the crystalline axes but not the junction
geometrical long axis. The TMR reaches ~ 1900% at 4K, corresponding to an
interfacial spin polarization of > 95% assuming identical interfaces. These
results show that uniaxial anisotropy is not necessary for large TMR, and lay
the groundwork for future improvements in TMR in manganite junctions.
