How to change font family in a levelplot using Lattice

Dear R users:

I want to assign a global font family to a levelplot such as par(family="serif") in traditional plotting. However, I can only change part of the text using

panel.text(x,y,"A",fontfamily="serif")
or scales=list(fontfamily="serif") to change the axis number font family.

How can I change the font family of xlab and ylab and the numbers shown on the legend of the levelplot?

Thanks in advance,
Bingzhang