  We propose a compact binary model for the fast radio burst (FRB) repeaters,
where the system consists of a magnetic white dwarf (WD) and a neutron star
(NS) with strong bipolar magnetic fields. When the WD fills its Roche lobe,
mass transfer will occur from the WD to the NS through the inner Lagrange
point. The accreted magnetized materials may trigger magnetic reconnection when
they approach the NS surface, and therefore the electrons can be accelerated to
an ultra-relativistic speed. In this scenario, the curvature radiation of the
electrons moving along the NS magnetic field lines can account for the
characteristic frequency and the timescale of an FRB. Owing to the conservation
of angular momentum, the WD may be kicked away after a burst, and the next
burst may appear when the system becomes semi-detached again through the
gravitational radiation. By comparing our analyses with the observations, we
show that such an intermittent Roche lobe overflow mechanism can be responsible
for the observed repeating behavior of FRB 121102.
