  We consider an exact expression for the 6j-symbol for the isosceles
tetrahedron, involving integrals over SU(2), and use it to write the two-point
function of 3d gravity on a single tetrahedron as a group integral. The
perturbative expansion of this expression is then performed with respect to the
boundary geometry using a simple saddle-point analysis. We derive the complete
expansion in inverse powers of the length scale and evaluate explicitly the
quantum corrections up to second order. Finally, we use the same method to
provide the complete expansion of the isosceles 6j-symbol with the explicit
phases at all orders and the next-to-leading correction to the Ponzano-Regge
asymptotics.
