I have written a symbolic matrix and I am trying to evaluate its matrix elements for a specific choice of the parameters:`H(k_, C1_, C2_, g_, t_, tprime_, L_, mu_) := {{-2 t Cos(k) - mu, -I g (Conjugate(C1) k^2 -Conjugate(C2))/(3 L)}, {I g (C1 k^2 - C2)/(3 L), -2 tprime Cos(k) - 3 mu}};`

But when I try to do it first of all symbolically with the command `H((1,1))`

,I get the following error:

```
During evaluation of In(85):= Part::partd: Part specification H((1,1)) is longer than depth of object.
Out(85)= H((1, 1))
```

Ideally, I need to evaluate matrix elements such as H((1,1)) for specific values of the variables on top of it.

I did not find a simple explanation for that.

Thank you for any help!