Hollywood star Sienna Miller

Sienna Miller has been pictured sunbathing topless with actor Rhys Ifans (left).The 'Factory Girl' actress, who has been enjoying a sun-drenched holiday with the 'Notting Hill' star on the Spanish party island of Ibiza, stripped off on a busy beach to ensure she got an even tan.Onlookers claim the pair seemed quite keen on one another and were spotted walking arm-in-arm along the picturesque shore.The day after they returned from Ibiza, Sienna, 25, and 39-year-old Rhys met for a drink in a trendy London bar.Earlier this month, it was reported Sienna - who was previously engaged to Hollywood heartthrob Jude Law - had fallen for her new co-star Sean Bean.The blonde beauty recently invited Sean to spend a romantic evening at her west London home and even cooked Sean a special beef stew.A source said: "She is completely mesmerised by Sean already. She has told friends that she can't help feeling transfixed by his green eyes and loves the fact that he is a real macho man."Sienna and Sean, 48, are due to start filming Oscar Wilde's 'A Woman of No Importance' in September.