  We report new measurements of the thermal expansion and thermo-optic
coefficients of RbTiOPO$_4$ (RTP) and KTiOPO$_4$ (KTP) crystals over the
temperature range 300-350 K. For RTP/KTP our coefficients of linear thermal
expansion at 305 K are: $\alpha_x=9.44/7.88\times 10^{-6}$/K,
$\alpha_y=12.49/9.48\times 10^{-6}$/K, $\alpha_z=-4.16/0.02\times 10^{-6}$/K.
Our normalized thermo-optic coefficients $\beta=(1/n)dn/dT$ at 632.8 nm and 305
K are: $\beta_x=5.39/3.78\times 10^{-6}$/K, $\beta_y=7.11/5.24\times
10^{-6}$/K, $\beta_z=12.35/9.34\times 10^{-6}$/K.
