Url display "&" instead of &

in polystat, i’m trying to set the url for clickthrough using composite. i don’t understand why when i set the url to: “https://link/cluster-load?var-DataSource=a&var-cluster=b” when i click on the composite it bring me to a page with this url “https://link/cluster-load?var-DataSource=a&var-cluster=b”, adding & and don’t bringing me to the right page (var-cluster for example is right using ${__composite_name} but when i clic on the composite i think that & makes it gone to the wrong page.