5 FTSE 100 Shares You Should Have Bought In January

January has been a remarkable month for the FTSE 100, which started the year by breaching the 6,000 level. Since then, the records have tumbled almost daily, and the top-tier London index has gone on to break 6,300 before falling back slightly to close yesterday on 6,277 points. That's a whopping 6.4% rise on the month.

But which of the FTSE 100's constituents have performed the best since the new year commenced? Here are five whose shares have appreciated nicely, but which may still be undervalued today:

Vodafone

Vodafone Group (LSE: VOD), a multinational mobile phone company with solid earnings, rising dividends, so much cash that it has been on a share buyback spree to return it to shareholders, a forecast dividend yield of over 6%, yet the shares languish on a price-to-earnings (P/E) ratio of only 11? Does that make sense to you? It doesn't to me, which is why I added Vodafone to the Fool's Beginners' Portfolio when investors in 2012 were shunning the company.

But with the advent of the new year, it looks like some common sense is returning, and the share price has started to pick up. Ending December on 154p, Vodafone shares rose during January by 19p (12.3%) to finish the month on 173p. You'd have done well to buy Vodafone in January, but does the price have further to go? Well, that P/E and dividend yield I quoted is current, after the month's price rise. Vodafone still looks cheap to me -- but you have to make your own decision.

Xstrata

The mining sector has had a tough year or two, with global commodities prices pushed down by slowing growth in China, but since late summer their share prices have started to pick up again. Xstrata (LSE: XTA) shares put on 129p (12.2%) to reach 1,188p during January, which is pretty typical of the big FTSE 100 miners, though Xstrata investors have been partly occupied by the done-and-dusted Glencore merger (now expected to happen by 15 March).

Analyst expectations for the year to 31 December put Xstrata shares on a P/E of 17, but that's with a fall in earnings per share (EPS) of more than 40% expected. Glencore is on a lower P/E of 13. The next couple of years should see EPS rebounding and P/E falling, and we're already hearing positive news of the Chinese economy.

SABMiller

Shares in brewer SABMiller (LSE: SAB) climbed 325p (11.5%) to 3,150p during January, which would have got you a nice little earner. But wait, the shares are on a forward P/E based on forecasts for the year to March 2013 of 21, with an expected dividend yield of only 2.1%. Can we really expect the shares to still be a good buy after January's rise?

Well, the thing that makes SABMiller special is that its share price has beaten the FTSE for 12 straight years, thanks to regular double-digit growth in earnings per share and a dominating position in its South African home market. Are you going to bet against that feat being repeated again this year? I'm not.

HSBC

If you'd bought HSBC (LSE: HSBA) shares, you'd have enjoyed a 71p (11%) rise to 717p since the start of the year, as the UK's banking sector started 2013 the way it ended 2012 -- heading back up. In fact, the HSBC share price is up more than 30% over the past 12 months, and is pretty much back to pre-crash levels.

After this impressive recovery, is HSBC's bull run over? Forecasts suggest not, with expectations for 2012 putting the shares on a P/E of 13 with a dividend yield of just under 4%. And if forecasts for the next two years are close, we should be looking at a P/E of 12 and a dividend yield of almost 5% by 2014 -- if the price does not move.

Unilever

Who'd have thought that good old safe stalwart Unilever (LSE: ULVR) would be the kind of company to put on 8.5% in just a month? Well, that's what it has just done, climbing 201p to 2,567p, in the month that the consumer brands giant reported a 10.5% rise in turnover for the year to December, with operating profit up 9%.

Forecasts for 2013 suggest a forward P/E of 18 with a dividend yield of under 3.5%, which many would consider overvalued for a maker of things like cleaning products. But a full 55% of Unilever's turnover now comes from emerging markets and, if they continue with rapid growth, that high valuation might turn out to be justified.

Finally, all of these companies pay dividends, and that can make a huge difference to the long-term value of a portfolio. Whether you take the income to live on or reinvest it in more shares, there's nothing wrong with good old cash, whatever your strategy.

And that's why I recommend the BRAND-NEW Fool report, "The Motley Fool's Top Income Share For 2013", in which our top analysts identify a share that they believe will provide handsome dividend income for years to come.

But it will only be available for a limited period, so click here to get your copy today.