how to make searchfield as mandatory in formelement

We need to make the searchfield label as mandatory  in a formelement.

GIven below is the code we have used. but not working.

new sap.ui.layout.form.FormElement({fields: [oSearch = new sap.ui.commons.SearchField("sf_srvcRecipient",{       
        value: "",
        enableListSuggest: false,
        layoutData: new sap.ui.layout.form.GridElementData({hCells: "5"})}
       )],
       label: new sap.ui.commons.Label("lb_srvcRecipient",{
        required: true, text: "Service Recipient", labelFor: oSearch
        })
      }),