NMR studies of superconducting Ba8AgxSi46-x (x=0 similar to 6)

NMR spectra of Si-29 and Ba-137 were measured in silicon clathrate compound s, Ba8AgxSi46-x (x=0 similar to6), to investigate their electronic properti es and superconducting mechanism. The measurement of the shift shows that t he sample with the higher superconducting transition temperature has the la rger density of states at the Si and Pa sites. In Ba8Si46, the Knight shift of Si sites has activation type plus constant temperature dependence betwe en 50 and 300 K. This demonstrates that the electrons at the Fermi level ar e thermally excited to the Si-46 conduction band states.