Minimal 2-matching-covered graphs

A perfect 2-matching M of a graph G is a spanning subgraph of G such that each component of M is either an edge or a cycle. A graph G is said to be 2-matching-covered if every edge of G lies in some perfect 2-matching of G . A 2-matching-covered graph is equivalent to a “regularizable” graph, which was introduced and studied by Berge. A Tutte-type characterization for 2-matching-covered graph was given by Berge. A 2-matching-covered graph is minimal if G − e is not 2-matching-covered for all edges e of G . We use Berge’s theorem to prove that the minimum degree of a minimal 2-matching-covered graph other than K 2 and K 4 is 2 and to prove that a minimal 2-matching-covered graph other than K 4 cannot contain a complete subgraph with at least 4 vertices.