Yes, you can! You have the option to pay extra contributions through Additional Voluntary Contributions (AVCs).
You may pay up to 100% of your Contribution Earnings in Scheme contributions and AVCs. However, if when you add the AVCs that you have paid in a year (and contributions to any other schemes) to the increase in the value of your pension, and they exceed the Annual Allowance (AA), you will have to pay tax at your marginal rate on the excess amount over the AA. For further information, please click here.