Creating Parent and Child Records in a Single Statement Using Foreign Keys

Account objAccount = new Account(Name='TestAccount',MyExtID__c='Ext_id');
Contact objContact = new Contact();
objContact.Account=new Account(MyExtID__c='Ext_id');
objContact.lastName='TestContact';
     
Database.SaveResult[] results = Database.insert(new SObject[] {
            objAccount, objContact });