Better alternative than ppf

You could go for Life insurance, mutual funds (if you don't want the income to be taxed) but In my view, PPF is the best just next to investment in a residential property

INVESTMENT should be based on our need and not just to save tax. Many a times we make investment purely to save tax and in such process we end up making incorrect investment.  To save tax of few rupees we make huge amount of investment which is purley unnecsary.

Now comes your question.. PPF is best option which gives tax free int. Plus you can withdraw half amount after 5th yr. However its not advisabe to invest full amount in PPF. You should also have adequate life cover and also medical cover also. Plus since your age is less so you have more risk taking capacity,  hence you can invest  in tax saving  Mutual fund. This way you can start building your corpus for retirement.

I short dont just invest in PPF(debt). Take adequate life cover and medical cover and also invest in equity and build adequate corpus for retirment and save tax also 

That was a good answer CA Shah