  We investigate experimentally the dynamic phase transition of a
two-dimensional active nematic layer interfaced with a passive liquid crystal.
Under a temperature ramp that leads to the transition of the passive liquid
into a highly anisotropic lamellar smectic-A phase, and in the presence of a
magnetic field, the coupled active nematic reorganizes its flow and
orientational patterns from the turbulent into a quasi-laminar regime aligned
perpendicularly to the field. Remarkably, while the phase transition of the
passive fluid is known to be continuous, our observations reveal intermittent
dynamics of the order parameter and the coexistence of aligned and turbulent
regions in the active nematic, a signature of discontinuous, or first order,
phase transitions.
