In studying compensated semimetals, the two-band model has proven extremely useful in capturing electrical conductivity under magnetic field, as a function of density and mobility of electronlike and holelike carriers. However, it rarely offers practical insight into magnetothermoelectric properties. Here, we report the field dependence of thermoelectric (TE) coefficients in a highly compensated semimetal ${\mathrm{NbSb}}_2$, where we find the Seebeck ($S_{xx}$) and Nernst ($S_{xy}$) coefficients increase quadratically and linearly with applied magnetic field, respectively. Such field dependence was predicted in previous work that studied a system of two parabolic bands, within semiclassical Boltzmann transport theory when the following two conditions are simultaneously met: ${\omega }_c\tau \gg 1$ and $tan{\theta }_H\ll 1$, where ${\omega }_c$ and $\tau$ refer to the cyclotron frequency and relaxation time, respectively, and ${\theta }_H$ is the Hall angle. Under these conditions, we find the field dependence of the TE coefficients directly provides a relation between the electronlike ($n_e$) and holelike ($n_h$) carrier densities, which in turn can be used to refine two-band model fitting. With this, we find the compensation factor ($\frac{\left|\mathrm{\Delta }n\right|}{n_e}$, where $\mathrm{\Delta }n=n_e-n_h$) of ${\mathrm{NbSb}}_2$ is two orders of magnitude smaller than what was found in unrestricted fitting, resulting in a larger saturation-field scale for magnetoresistance. Within the same framework of the semiclassical theory, we also deduce that the thermoelectric Hall angle $tan{\theta }_{\gamma }=\frac{S_{xy}}{S_{xx}}$ can be expressed as $(\frac{\mathrm{\Delta }n}{n_e}\times {\omega }_c\tau {)}^{-1}$, which serves as a parameter to predict the degree of compensation. Our findings offer crucial insights into identifying empirical conditions for field-induced enhancement of TE performance and into engineering-efficient thermoelectric devices based on semimetallic materials.

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• Electrical conductivity
• Electrical properties
• Magnetotransport
• Thermoelectric effects
• Semimetals
• Transport techniques