Properties of compounds of type NaxSi46 and NaxSi136

A qualitative account is given of the electrical and magnetic properties of compounds of the type Na_xSi₁₃₆. It is suggested that a metal-insulator transition takes place with decreasing x. It is conjectured that in sintered powders the resistance is due to amorphous contacts between grains, leading to a resistivity proportional to $\text{A}\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$.