E-voting: public tallying vs. vote selling
The second property is formally called receipt freeness.  Any voting system based on probabilistic encryption cannot be receipt free, because the voter uses  a random value to construct the vote, this random value can serve as a receipt.
The solution given to this problem is by having an authority create the vote and the voter simply selects it from a presented list.
The first protocol to achieve this is as far as I know is the one described in the paper Receipt-free secret-ballot elections from Benaloh and Tuinstra. A more widely used example is  Efficient receipt-free voting based on homomorphic encryption from Hirt and Sako. 
You can check these references especially the second one on details about how to achieve verifiability.