Electrical and magnetotransport properties of (La13 Sm23) 23 A13 Mn O3 (A=Ca, Sr, and Ba) compounds, synthesized by the citrate gel route, have been investigated. These compounds crystallize in an orthorhombic structure (space group Pnma). Semiconducting-like behavior is observed only in Ca-substituted sample while Ba and Sr-substituted samples show metal-insulator type transition. The high and weakly temperature dependent magnetoresistance at low temperature, thermal irreversibility in field-cooled and zero-field-cooled magnetization, and nonsaturating magnetization behavior are expected in systems with electronic phase separation. The cationic size disorder by varying alkaline earth ions causes the electronic phase separation. © 2005 American Institute of Physics.