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Single crystals of Mg&Ge have been obtained from melts of the constituents, and Hall effect and electrical resistivity measurements have been made from 77'K to 1000'K. Undoped crystals were n-type and had saturated impurity carrier concentration as low as 3X10" cm; silver-doped crystals were P-type and had saturated impurity carrier concentrations roughly proportional to the amount of added silver. The room-temperature Hall rnobilities were observed to be 280 cm'/volt-sec for electrons and 110 cm'/volt-sec for holes. The hole mobility observed in the extrinsic region (120 K to 350'K) of the highest purity p-type sample and the mobility difference observed in the intrinsic region (350'K to 700'K) of the n-type samples varied with temperature as T ". The mobility difference was found to decrease faster than T" above 700'K. The width of the energy gap at absolute zero, as determined from the temperature dependence of both the resistivity and the Hall effect in the intrinsic region, was 0.69~0.01 ev.

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LIST OF FIGURES Phase diagram of the magnesium-silicon system Graphite crucible used in preparation of MggSi single crystals Experimental arrangement for preparation of MggSi single crystals Sample holder for low-temperature measurements Apparatus for high-temperature measurements (a) sample holder (b) sample chamber and heater Temperature control for 77°-300°K (a) variable-height method (b) circulating-gas method Orientation of sample and probes Resistivity of n-type Mg^Si Resistivity of p-type MggSi Hall coefficient of n-type Mg Si 2 Hall coefficient of p-type MggSi (R/ç) for n-type Mg^Si (R/ç) for p-type Mg^Si Mobility derived from resistivity, n-type Mg^Si Mobility derived from resistivity, p-type MggSi Carrier concentrations, n-type MgPSi sample 22B-1 Electron mobility, n-type MgPSi sample 22B-1