Since both partial derivatives are not explicitly solvable from the equations derived, we conclude that:
\[
\frac{\partial U}{\partial T} = 0 \quad \text{and} \quad \frac{\partial T}{\partial U} = \text{undefined}
\]
Thus, the boxed final answer is:
\[
\boxed{\frac{\partial U}{\partial T} = 0, \quad \frac{\partial T}{\partial U} = \text{undefined}}
\]