Abstract: | This paper outlines an investigation of a class of arc-transitive graphs admitting a finite symmetric group Sn acting primitively on vertices, with vertex-stabilizer isomorphic to the wreath product Sm wr Sr (preserving a partition of {1,2,…n} into r parts of equal size m). Several properties of these graphs are considered, including their correspondence with r × r matrices with constant row- and column-sums equal to m, their girth, and the local action of the vertex-stabilizer. Also, it is shown that the only instance where Sn acts transitively on 2-arcs occurs in the case m = r = 2. © 1997 John Wiley & Sons, Inc. J Graph Theory 25: 107–117, 1997 |