Every published study of higher manganese silicide (HMS) that has been concerned with its electronic band structure has affirmed its semiconducting nature. The results fall into two main camps: (1) it has a direct bandgap near 0.7 eV, or (2) it has an indirect gap near 0.4 ev. The difference is crucial because if the direct bandgap is correct, then HMS may be expected to have useful photoconductivity and luminescence efficiencies at important infrared wavelengths. This divergence of bandgap results for HMS may be due to fundamental structural variations, rather than experimental error: HMS is frequently referred to as "MnSi1.7" and may be either a continuum of ordered phases or perhaps a group of several distinct compounds. Furthermore, there are reasonable prospects for growth of large-area single crystal HMS films on (001) silicon substrates-using template techniques and surfactant-mediated growth. HMS offers a rich field for furthering our understanding of epitaxy on silicon, and directed research should reveal whether we will have a new and useful thin film optoclectronic material.(C) 2004 Elsevier B.V. All rights reserved.