  Within the framework of HQET,
$\Lambda_{b}\rightarrow\Lambda_{c}\tau\bar{\nu}_{\tau}$ and
$\Omega_{b}\rightarrow\Omega_{c}^{(*)}\tau\bar{\nu}_{\tau}$ weak decays are
studied to the order of $1/m_c$ and $1/m_b$. Helicity amplitudes are written
down. Relevant Isgur-Wise functions given by QCD sum rule and large $N_c$
methods are applied in the numerical analysis. The baryonic R-ratios
$R(\Lambda_c)$ and $R(\Omega_c^{(*)})$ are obtained.
