  We report magnetic and thermodynamic properties of single crystal
$\alpha$-RuCl$_3$, in which the Ru$^{3+}$ ($4d^5$) ion is in its low spin state
and forms a honeycomb lattice. Two features are observed in both magnetic
susceptibility and specific heat data; a sharp peak at 7~K and a broad hump
near 10-15K. In addition, we observe a metamagnetic transition between 5~T and
10~T. Our neutron diffraction study of single crystal samples confirms that the
low temperature peak in the specific heat is associated with a magnetic order
with unit cell doubling along the honeycomb (100) direction, which is
consistent with zigzag order, one of the types of magnetic order predicted
within the framework of the Kitaev-Heisenberg model.
