An alloy cluster containing a 13-atom core, with a composition Ag 7Au 6(H 2MSA) 10 (H 2MSA= mercaptosuccinic acid) was synthesized from silver clusters by a galvanic exchange reaction. The clusters were characterized by several spectroscopic and microscopic methods. The alloy cluster shows luminescence with a quantum yield of 3.5 × 10 -2 at room temperature. Theoretical calculations for Ag 7Au 6(SCH 3) 10 suggest a distorted icosahedral core. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.