How to add aliases in the template?

I would like to add aliases in my template.
I tried “+roam_aliases:”, like this:

(setq org-roam-capture-templates
          '(
            ;; other templates 
            ("r" "ref" plain
             "%?"
             :if-new (file+head "./ref_notes/${slug}.org"
                                "#+title: ${title}\n#+roam_aliases: ${citekey}\n")
             :unnarrowed t)))

But it was added outside the PROPERTY block. So the file cannot be found using “org-roam-node-find”.