${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$ is a van der Waals material composed of one-dimensional chains that exhibits an exceptionally large thermoelectric power factor below room temperature. However, since this material has only been available as acicular microcrystals, experimental exploration of the electronic properties underlying its giant thermoelectric performance has remained challenging. In this study, we quantitatively evaluate the electronic anisotropy of ${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$ by combining micro-spot angle-resolved photoemission spectroscopy with transport measurements on focused-ion-beam-processed samples. Angle-resolved photoemission spectroscopy shows anisotropic band dispersions along and perpendicular to the crystallographic $c$ axis. Consistently, transport measurements demonstrate that the resistivity perpendicular to the $c$ axis is approximately five times larger than that along the $c$ axis at 200 K. Hall measurements further provide estimates of the carrier concentration, mobility, and an effective band gap of 0.134 ± 0.034 eV. These results reveal the weakly one-dimensional electronic and transport character of ${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$, providing microscopic insight into the origin of its giant thermoelectric response and highlighting the role of moderate electronic dimensionality in enhancing thermoelectric performance.

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• Charge
• Electrical conductivity
• Electronic structure
• Hall effect
• Seebeck effect
• Thermoelectric effects
• Transport phenomena
• 1-dimensional systems
• van der Waals systems
• Angle-resolved photoemission spectroscopy
• Focused ion beam
• Hall bar