Random order with pagination on archive page

Hi,

I currently display one post per archive page with pagination (Next & Previous links).

I wish to randomize the order of the posts. I’m using orderby:rand which works well but only on the first archive page…

The problem is that if I click on Next, it will randomize the posts again… Doesn’t make any sense.

How to randomize the posts order on archive page only once and using the pagination links ?

Thanks.