yet alone

Conjunction

let alone

1. (idiomatic) Much less; to say nothing of; used after one negative clause to introduce another, usually broader and more important clause, whose negation is implied by the negation of the first. However either of these instances mentioned can be applied with the use of let alone.
   • He couldn't boil water, let alone prepare a dinner for eight.
2. (idiomatic, rare) Not to mention, as well as; used after one item, to introduce a further item which is entailed by the first.
   • At the end of another ten years, let alone sixty, we are likely to see a very different pattern in the realm of British passenger locomotive power.1957 July, Cecil J. Allen, “British Locomotive Performance and Performance during Sixty Years”, in Railway Magazine, page 496

See all 4 meanings of let alone