Symmetry Control of Mutually Thermoelectric Conversion in Rutile RuO ₂

ABSTRACT Manipulating thermoelectric conversion is vital for thermal monitoring and management, which requires a tunable order coupled with thermoelectric coefficients. Previous studies concentrated on magnetic order, leading to discoveries such as the anomalous Nernst effect and the anisotropic magneto‐Peltier effects. In contrast, the dependence on crystal order remains largely unexplored. Here, we demonstrate that crystal symmetry can be harnessed to modulate thermoelectric effects in rutile RuO 2 films. The broken 4‐fold rotational symmetry induces anisotropic Peltier and Seebeck tensors with unequal diagonal and finite off‐diagonal elements, thereby enabling longitudinal Peltier cooling without P–N junctions and field‐free transverse thermoelectric interconversion without net magnetization. We use lock‐in thermography to visualize current‐induced thermal transport (charge‐to‐heat conversion), which exhibits crystal orientation‐dependent Peltier cooling and heating patterns. Conversely, the transverse heat‐to‐charge conversion is also detected, which follows a sinusoidal dependence on the crystal orientation. Unlike the magnetic order, crystal‐order‐dependent thermoelectric effects are not constrained by spin‐orbit coupling, allowing higher efficiency by an order of magnitude than ferromagnetic films. Our findings not only highlight the significant role of crystal symmetry in thermoelectric interconversion but also open new avenues for developing efficient on‐chip temperature sensors and heat harvesting technologies.