  We report the discovery of a substellar companion to 2MASS J02192210-3925225,
a young M6 $\gamma$ candidate member of the Tucana-Horologium association (30 -
40 Myr). This L4 $\gamma$ companion has been discovered with seeing-limited
direct imaging observations; at a 4" separation (160AU) and a modest contrast
ratio, it joins the very short list of young low-mass companions amenable to
study without the aid of adaptive optics, enabling its characterization with a
much wider suite of instruments than is possible for companions uncovered by
high-contrast imaging surveys. With a model-dependent mass of 12-15MJup, it
straddles the boundary between the planet and brown dwarf mass regimes. We
present near-infrared spectroscopy of this companion and compare it to various
similar objects uncovered in the last few years. The J0219-3925 system falls in
a sparsely populated part of the host mass versus mass ratio diagram for
binaries; the dearth of known similar companions may be due to observational
biases in previous low-mass companion searches.
