How to make autocomplete search by an entity field instead of by name?
Create a new view with the display type "Entity Reference"
Add "Fields", "Filter criteria" and "Sort criteria" like in any other normal view
Under "Format > Settings", select the fields you want to be searchable
Under "Show > Settings", select the fields you want to show as search result
Save the view
Now visit "Structure > Content type > NODETYPE > Manage fields"
Edit your entity reference field, set the "Reference Method" to "Views: filter by an entity reference view"
Select your previously created view