  We investigate the macroscopic quantum coherence of a spin-1 Rb condensate
confined in an anisotropic potential. Under the single-mode approximation, we
show that the system can be modeled as a biaxial quantum magnet due to the
interplay between the magnetic dipole-dipole interaction and the anisotropic
potential. By applying a magnetic field along the hard-axis, we show that the
tunneling splitting oscillates as a function of the field strength. We also
propose an experimental scheme to detect the oscillatory behavior of the
tunneling splitting by employing the Landau-Zener tunneling.
