  We report a unique feature of magnetic field Feshbach resonances in which
atoms collide with non-zero orbital angular momentum. P-wave ($l=1$) Feshbach
resonances are split into two components depending on the magnitude of the
resonant state's projection of orbital angular momentum onto the field axis.
This splitting is due to the magnetic dipole-dipole interaction between the
atoms and it offers a means to tune anisotropic interactions of an ultra-cold
gas of atoms. A parameterization of the resonance in terms of an effective
range expansion is given.
