A new form of graphitic cages in nanometer scale, rectangular parallelopiped (or cube), was produced by are evaporation of a carbon electrode containing calcium or strontium. Both the empty and the filled rectangular nanocapsules averaging 20-100 nm in size were formed, though the empty ones were dominant. The rectangular cages were made up of multi-walled (5-20 layers) graphitic carbon. The encapsulated materials were beta-CaC2(tetragonal), gamma-CaC2(cubic) and delta-CaC2 (monoclinic) for C/Ca evaporation, and beta-SrC2 (tetragonal) and metallic Sr for C/S revaporation. (C) 1998 Elsevier Science B.V. All rights reserved.