The unit group of a partial Burnside ring relative to the Young subgroups of the symmetric group SnSn on n letters is included in the image by the tom Dieck homomorphism. As a consequence of this fact, the alternating character νnνn of SnSn is expressed explicitly as a ZZ-linear combinations of permutation characters associated with finite left SnSn-sets Sn/YSn/Y for the Young subgroups Y.Mathematics Subject Classification. Primary 19A22, Secondary 20B35; 20C15; 20C3