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To mitigate the temperature sensitivity of photonic devices, materials with a negative thermo-optical coefficient (TOC) are integrated to optical waveguides. However, previously reported waveguides are made athermal at only one wavelength. In this paper, we theoretically propose a new broadband athermal waveguide, which consists of TiO₂ with a negative TOC and SiC with a positive TOC in its core. This composite core shows a near-zero broadband effective TOC, i.e., ±1x10^-6/K over a 780-nm bandwidth from 1280 to 2060 nm. Furthermore, it also has low anomalous dispersion, from 66 to 329 ps/nm/km in the same wavelength range. This new athermal waveguide, when used to form microresonators, enables us to achieve broadband nonlinear applications with negligible intra-cavity thermal dynamics on a chip. We also show that the proposed waveguide can be tightly bent without suffering from a large bending loss/substrate leakage, which is suitable for dense integration.