Are you ignoring these chunky dividend yields from the FTSE 100?

With cash savings account interest rates at all-time lows, many investors are turning to dividend stocks to boost their investment returns. Here's a look at three FTSE 100 companies paying sizeable dividends to shareholders.

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Marks and Spencer Group

There's no doubt many investors have thrown in the towel at Marks and Spencer Group (LSE: MKS) in the last 15 months. The share price has fallen from 600p in May 2015 to below 300p in June this year, and is down a dismal 23% year to date. Furthermore, in Q2 M&S underperformed the FTSE 100 by 28%, its worst relative quarterly underperformance since the FTSE 100 was created in 1984. Sentiment towards the high street stalwart is clearly very low right now.

However, despite the fact the retailer's clothing sales have been woeful in recent years and that profits at the company are roughly 20% lower than they were 20 years ago, the company is still paying its shareholders a dividend and a significant one at that. It paid out dividends of 18.7p per share for FY2016 as well as a 'special dividend' of an extra 4.6p per share for a total yield of 6.8%, not bad for a struggling retailer.

Of course, the question that arises whenever a yield is this high is whether the dividends are sustainable. Well the good news is that city analysts seem to believe they are sustainable, at least for the next few years, with consensus dividend forecasts of 21p per share for FY2017 and FY2018, a yield of an excellent 6.1%.

Furthermore, analysts at Morgan Stanley believe that Marks and Spencer may be due for a rerating, pointing out that as 60% of UK sales are now coming from the strongly performing food division, it's only a matter of time until investors view M&S as a highly performing food retailer, rather than a struggling clothing retailer.

Sky

Another company that has seen a dramatic share price fall this year is pay-TV specialist Sky (LSE: SKY).

Not generally known as a high dividend stock, the 23% fall in the share price this year has created an opportunity for income investors, with the yield now sitting at a healthy 3.9%.

Over the past five years, Sky's dividend has grown at an annualised rate of over 10%, and while the city forecast dividends to remain flat in FY2017 at 34p per share, consensus estimates point to dividend growth of 9% for 2018 to 37p per share.

Annual results in July showed revenue and adjusted operating profit growth of 7% and 12% respectively, and with the company trading on a P/E ratio of 15.3 times next year's earnings, now could be a good time to take advantage of this year's share price weakness to obtain a larger than usual dividend yield.

United Utilities Group

Utility stocks may not be exciting but they can certainly make excellent dividend stocks.

United Utilities Group(LSE: UU) is a case in point, with the company paying out 38p per share in dividends for FY2015, a solid yield of 4%.

United's dividend policy is to target a dividend growth rate of at least RPI inflation each year through to 2020 and dividend growth in the last five years has averaged 5.1% per year on an annualised basis.

For investors looking for a low volatility income stock, United Utilities Group could be worth a look.

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Edward Sheldon owns shares in Sky. The Motley Fool UK has recommended Sky. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.