How can I permute indices in tensor fields on manifolds? I would like to define the following (0,4) tensor
$R_{abcd} = g_{a[c}g_{d]b}$
but I can't find an "easy" way (apart from assigning all the components bruteforce with some for loop, I guess). I presume there should be an "ovious" way of doing that but I cannot find it. Thanks.
