The effects of full anisotropy of the silicon carbide (SiC) band structure together with alignment of the conduction band valleys, nanocrystal geometry, and external field, upon 4H-and 6H-SiC polytypes is addressed in this work. Our calculations show that the combination of shape, electric field direction and band structure anisotropy may have strong consequences for confined electron energies SiC nanocrystals (NCs). The break of degeneracy under specific conditions will influence the design of device applications and advances in SiC nanocrystal-based technology. (C) 2004 Elsevier B.V. All rights reserved.