  Using flow visualizations in Couette geometry, we demonstrate the existence
of Taylor-like vortices in the shear-banding flow of a giant micelles system.
We show that vortices stacked along the vorticity direction develop
concomitantly with interfacial undulations. These cellular structures are
mainly localized in the induced band and their dynamics is fully correlated
with that of the interface. As the control parameter increases, we observe a
transition from a steady vortex flow to a state where pairs of vortices are
continuously created and destroyed. Normal stress effects are discussed as
potential mechanisms driving the three-dimensional flow.
