[en] The influence of transverse magnetic field on the liquid-solid interface stability and morphology has been investigated in directionally solidified Al-0.85wt%Cu alloy. Experimental results show that the transverse magnetic field causes the interface to be instable and the interface shape to be depressed on one side along the radius. The interface instability increases with increasing magnetic field. Increasing the solidification velocity reduced extent of interface destabilization by the magnetic field. The depression of the interface with the magnetic field is more dramatic at low solidification velocities. These phenomena are attributed to the thermoelectromagnetic convection (TEMC) on the interface and cellular scale.