[Tex/LaTex] A letter or symbol above a tensor

Question

I would like to put a letter, e.g. \lambda, above a tensor, e.g. Riemann tensor, by which I mean a tensor that is function of \lambda.
I use \tensor and \overset command to construct this object. Here the code:

\documentclass{letter}
\usepackage{amsmath}
\usepackage{tensor}
\begin{document}
\[ \overset{\lambda}{\tensor{R}{^a_b_c_d}} \]
\end{document}

But that's not what I searching for, because the \lambda stand over entire tensor and not over the letter of tensor (here R).
Can somebody help me?

Answer 1

You can use the following "dirty" trick with \vphantom

\overset{\lambda}{R}\tensor{\vphantom{R}}{^a_b_c_d}

This works with the package \tensor.

MWE

\documentclass{letter}
\usepackage{amsmath}
\usepackage{tensor}
\begin{document}
\[ \overset{\lambda}{R}\tensor{\vphantom{R}}{^a_b_c_d} \]
\end{document}