A series of Sm(Fe1-xMnx)2Si2 polycrystalline samples (x=0, 0.25, 0.5, 0.75 and 1) has been prepared, characterized and studied in detail by means of specific heat (C), magnetization (M) and ac susceptibility measurements in the temperature range T=2-350K and in magnetic fields (B) up to 9T. Here we present selected results focused on the anomalous magnetic behavior of Sm(Fe0.5Mn 0.5)2Si2 and Sm(Fe0.75Mn 0.25)2Si2. © 2004 Elsevier B.V. All rights reserved.