  Layered IV-VI$_2$ compounds often exist in the CdI$_2$ structure. Using the
evolution algorithm and first-principles calculations, we predict a novel
layered structure of silicon ditelluride (SiTe$_2$) that is more stable than
the CdI$_2$ phase. The structure has a triclinic unit cell in its bulk form and
exhibits the competition between the Si atoms' tendency to form tetrahedral
bonds and the Te atoms' tendency to form hexagonal close-packing. The
electronic and vibrational properties of the predicted phase are investigated.
The effective mass of electron is small among 2D semiconductors, which is
beneficial for applications such as field-effect transistors. The vibrational
Raman and IR spectra are calculated to facilitate future experimental
investigations
