Silicon clathrate compounds are Si analogs of carbon cluster C₆₀; those consist of polyhedral cages of Si₂₀ and Si₂₄, which are linked three dimensionally by sharing faces. The Barium containing silicon clathrate compound, Na_xBa_ySi₄₆, shows superconductivity below 4 K. This is the first superconductor with a sp³-Si network. Silicon clathrate compounds are prepared from Zintl phases containing [Si₄]^4- cluster anions. Another kind of Zintl phase, CaSi₂ contains corrugated Si layers with Ca atoms between them. A layer structured polysilane (SiH)_n was derived from CaSi₂ by removing Ca in a concentrated HCl solution at -30°C. The polysilane is a semiconductor with a band ga of about 2.5 eV.