Barathea wool is considered the classic choice for formal dinner suits. Heavier than anything you'll find on today's high street, a good barathea will last a lifetime and never look out of place. Vintage barathea DJs are widely available, quality is routinely excellent, and so is value for money.
A velvet dinner jacket is a more 'dandy' alternative, perhaps. Originally derived from the smoking jacket and often still described as such. Silk-velvet examples are highly sought-after, and rightly so.