Electrical conductivity, thermopower, and Hall effect of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ti</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">AlC</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>,</mml:mo></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ti</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">AlN</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>,</mml:mo></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ti</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">SiC</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

In this paper we report on the thermopower and electrical conductivities of ${\mathrm{Ti}}_{4}{\mathrm{AlN}}_{2.9}$ and ${\mathrm{Ti}}_{3}{\mathrm{Al}}_{1.1}{\mathrm{C}}_{1.8}$ in the 300--850 K temperature range. We also measured the room temperature Hall effect in ${\mathrm{Ti}}_{3}{\mathrm{SiC}}_{2},$ ${\mathrm{Ti}}_{4}{\mathrm{AlN}}_{2.9},$ and ${\mathrm{Ti}}_{3}{\mathrm{Al}}_{1.1}{\mathrm{C}}_{1.8}.$ Based on these results we conclude that holes are the majority carriers at room temperature in ${\mathrm{Ti}}_{3}{\mathrm{Al}}_{1.1}{\mathrm{C}}_{1.8}$ and ${\mathrm{Ti}}_{4}{\mathrm{AlN}}_{2.9}.$ At higher temperatures free electrons contribute to the transport properties. ${\mathrm{Ti}}_{3}{\mathrm{SiC}}_{2}$ is a mixed conductor wherein the concentrations and mobilities of the free electrons are, respectively, equal to those of the holes over an extended temperature range. The high conductivity of ${\mathrm{Ti}}_{3}{\mathrm{SiC}}_{2}$ is due to the presence of a large concentration of charge carriers. The lower conductivity of ${\mathrm{Ti}}_{3}{\mathrm{Al}}_{1.1}{\mathrm{C}}_{1.8}$ is due to a dearth of charge carriers. The even lower conductivity of ${\mathrm{Ti}}_{4}{\mathrm{AlN}}_{2.9}$ is attributed to a reduced mobility, most probably due to vacancy scattering of the charge carriers.

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