/sp/fields&quot;;

const sp = spfi(...);

const list = await sp.web.lists.getByTitle(&quot;My Lookup List&quot;)();
// create a new lookup field called 'My Field' based on an existing list 'My Lookup List' showing 'Title' field in web.
const field = await sp.web.fields.addLookup(&quot;My Field&quot;, { LookupListId: list.data.Id, LookupFieldName: &quot;Title&quot; });
// create a new lookup field called 'My Field' based on an existing list 'My Lookup List' showing 'Title' field in list 'My List'
const field