Transport Properties of the Binary Type I Clathrate K ₈ Ge ₄₄ □ ₂

We report the synthesis and low‐temperature electrical resistivity, Seebeck coefficient, and thermal conductivity of the binary type I clathrate K ₈ Ge ₄₄ □ ₂ (□=Ge framework vacancy). Electrical resistivity measurements indicated metallic or heavily doped semiconductor behavior, while the Seebeck was relatively high at −77 μV/K at room temperature. The thermal conductivity was very low, on the order of 1 W/m K at room temperature. This work is part of a continuing effort to investigate new compositions in open‐structured and guest‐framework materials for potential thermoelectric applications.