How do you manage exponential tenor?

Of course, one could do it, but what is the best way?

Consider this example:

T_{ijmn}

I want to combine indices i by m and j by n, then put it into a matrix form and take exponential,

Matrix M=T_{im;Jn} ; M=exp(M);

then put M back into original T

M_{p;q}-------------->T1

It should have the same indices as original T.

T1------------------------->T_{ijmn}

### Is it any function to put Itensor into a matrix and vice versa?

The same is the case for eigval decomposition (for general matrices) and....