By vacuum-melted and cast in three kinds of mold made of metal, graphite and sand, the melts of Al-35%La alloy were cast with different solidification velocities. With the method of X-ray diffraction and SEM, a novel dendrite structure has been found in Al-35%La alloy. Experimental results show that there are some primary and secondary diphase dendrites in the microstructure with large cooling rate in the molds of metal and graphite; and there is only some primary diphase dendrite in the microstructure with low cooling rate in the sand mold, and its mechanisms of the formation of diphase dendrites have been discussed in detail. (C) 2012 Elsevier B.V. All rights reserved.