  We characterize the irreducible representations of the general linear group
GL(V) that have multiplicity 1 in the direct sum of all Schur modules of a
given exterior power of V. These have come up in connection with the relations
of the lower order minors of a generic matrix. We show that the minimal
relations conjectured by Bruns, Conca and Varbaro are exactly those coming from
partitions of single exterior type.
