We report on the detailed crystal structure and superconducting properties in the single-crystalline SrAlSi by means of synchrotron Xray diffraction technique and systematic magnetization measurements. Although SrAlSi exhibits a clear no sign of superlattice reflection, the anisotropic parameter for magnetic response in SrAlSi is almost equivalent to that of superstructured CaAlSi. It is inferred from these results that the electronic ground state in SrAlSi shows quasi-two-dimensional characteristics, and its dimensionality is irrelevant to the superstructured system. (c) 2007 Elsevier B.V. All rights reserved.