To contribute to the understanding of the Al-Fe-Mn-Si system, an exhaustive analysis of the intermetallic phases formed during thermal analysis experiments and specific isothermal treatments was carried out. In this work, three different phases were identified: the extensively reported β and α phases and the τh phase. The τh phase has been reported for the ternary Al-Fe-Si system, but not for the quaternary Al-Fe-Mn-Si system. Nonetheless, the present results suggest that the formation of the τh phase upon solidification of the alloy can be stabilized in the quaternary Al-Fe-Mn-Si system, with respect to the monoclinic θ-Al3Fe phase in the ternary Al-Fe-Si system, due to the Mn addition. The τh phase was unambiguously identified with the help of complementary techniques such as SEM/EDS, X-ray diffraction and Mössbauer spectroscopy. © 2010 Elsevier Ltd. All rights reserved.