splitting field of a polynomial

[Mathias Lederer <csab2185@uibk.ac.at>]

I would like to do some calculations in the splitting field of a
polynomial, so I thought pari/gp would be the right software for this. 

I imagined that there would be a function that gives a Q-basis of the
splitting field once the polynomial is given. But I've been searching
hard and I haven't found anything but nf and so on, which does not
perform what I want: It gives only Q[x], where x is a zero of the
irreducible) polynomial, and not Q[x1,...,xn], where x1,...,xn are all
the zeros of the polynomial. 

Is the any function that handles this?