  In this work, we demonstrate a C-band shear-horizontal surface acoustic wave
(SH-SAW) resonator with high electromechanical coupling (kt2) of 22% and a
quality factor (Q) of 565 based on a thin-film lithium niobate (LN) on silicon
carbide (SiC) platform, featuring an excellent figure-of-merit (FoM = kt2*Q )
of 124 at 6.5 GHz, the highest FoM reported in this frequency range. The
resonator frequency upscaling is achieved through wavelength ($\lambda$)
reduction and the use of thin aluminum (Al) electrodes. The LN/SiC waveguide
and synchronous resonator design collectively enable effective acoustic energy
confinement for a high FoM, even when the normalized thickness of LN approaches
a scale of 0.5$\lambda$ to 1$\lambda$. To perform a comprehensive study, we
also designed and fabricated five additional resonators, expending the
$\lambda$ studied ranging from 480 to 800 nm, in the same 500 nm-thick
transferred Y-cut thin-film LN on SiC. The fabricated SH-SAW resonators,
operating from 5 to 8 GHz, experimentally demonstrate a kt2 from 20.3% to 22.9%
and a Q from 350 to 575, thereby covering the entire C-band with excellent
performance.
