A new silicon clathrate compound containing barium, (Na, Ba),Si46, becomes a type-II superconductor with a critical temperature (T,) of about 4 K. In the compound, the silicon atoms are bonded tetrahedrally with about the same bond distances as in ordinary cubic diamond Si, but form 12and 14-hedral cages which are linked by shared faces. The metal atoms are located in the center of the polyhedra. This is the erst superconductor consisting of a Si sp' covalent network.PACS numbers: 74. 10.+v, 61.66.Fn, 74.70.Ad Silicon and carbon are often discussed in comparison with each other in terms of the same group-IV elements.As for elemental carbon, there are two allotropes, diamond and graphite, and recently fullerene has been added as a new member [1]; only the diamond type structure is known for elemental silicon. The recent discovery

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A series of bithiophene derivatives bearing an intramolecular monosilanylene or disilanylene bridge between the β,β‘-positions were synthesized, and their properties were investigated. UV spectral and cyclic voltammetric analyses of the silicon-bridged bithiophenes indicated that they have lower lying LUMOs, relative to those for bithiophene and methylene bridged bithiophenes, probably due to σ*−π* interaction between the silicon atom(s) and bithiophene π-orbitals, in good agreement with the results of theoretical calculations using simplified model compounds based on RHF/6-31G. The silicon-bridged bithiophenes exhibit high electron-transporting properties, and triple-layer-type electroluminescent (EL) devices, using the silicon-bridged bithiophenes, tris(8-quinolinolato)aluminum(III) complex (Alq), and N,N‘-diphenyl-N,N‘-di-m-tolylbiphenyl-4,4‘-diamine (TPD) as the electron-transporting, emitting, and hole-transporting layers, respectively, emitted strong EL.

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