Elastic Tensor of Sr${}_2$RuO${}_4$

The six independent elastic constants of Sr${}_2$RuO${}_4$ were determined using resonant ultrasound spectroscopy on a high-quality single-crystal specimen. The constants are in excellent agreement with those obtained from pulse-echo experiments performed on a sample cut from the same ingot. A calculation of the Debye temperature using the measured constants agrees well with values obtained from both specific heat and M"{o}ssbauer measurements.