  Microwave experiments along all three directions of the spin-density-wave
model compound (TMTSF)$_2$PF$_6$ reveal that the pinned mode resonance is
present along the $a$ and $b^{\prime}$ axes. The collective transport is
considered to be the fingerprint of the condensate. In contrast to common quasi
one-dimensional models, the density wave also slides in the perpendicular
$b^{\prime}$ direction. The collective response is absent along the least
conducting $c^*$ direction.
