  Susceptibility, specific heat, and muon spin rotation measurements on
high-quality single crystals of $\rm Na_{0.82}CoO_2$ have revealed bulk
antiferromagnetism with N\'{e}el temperature $\rm T_N = 19.8 \pm 0.1$ K and an
ordered moment perpendicular to the $\rm CoO_2$ layers. The magnetic order
encompasses nearly 100% of the crystal volume. The susceptibility exhibits a
broad peak around 30 K, characteristic of two-dimensional antiferromagnetic
fluctuations. The in-plane resistivity is metallic at high temperatures and
exhibits a minimum at $\rm T_N$.
