A route of formation of SiH3AlH radical via insertion of the ground-state Al((2)p) into SiH4 and subsequent rearrangements to various primary insertion product isomers including more stable SiH2AlH2 radical are predicted from the ab initio single-reference CCSD(T) and multi-reference MRMP2 calculations. For the insertion reaction, the lowest energy doublet ((2)A') potential energy surface is studied within C-s symmetry. Special attention is paid to the weakly bound Al center dot center dot center dot SiH4 complexes formed in the initial stage of the reaction. The results presented are of relevance to recent matrix studies on reactivity of the Al/SiH4 system. (c) 2006 Elsevier B.V. All rights reserved.