In a commercial Al-7.0Si-0.38Mg cast alloy (A356) with 0.20wt% Fe, added Mn modifies acicular beta-Al5FeSi particles to less acicular alpha-Al(Mn,Fe)Si in both crystallization and precipitation conditions. The crystal structure of alpha-Al(Mn,Fe)Si changes from body-centered cubic (bcc)/ simple cubic (sc) to Pm3 structures in response to an increase in the bulk Mn content of the alloy. The alpha-Al(Mn,Fe)Si particles (50-200nm) precipitate during solution treatment and their precipitation temperature is about 485 degrees C in the as-cast condition. (c) 2006 Elsevier B.V. All rights reserved.