Yes, you can.
ISA rules state that you can only pay into a single stocks and shares ISA each tax year.*
However, with IG you can invest in that single stocks and shares ISA through two separate account types at once: share dealing and/or an IG Smart Portfolio.
This means that if it suits your investment strategy to do so, you can open an IG Smart Portfolio ISA and share dealing ISA in the same tax year and split your annual allowance between them.
Remember, you are free to open an additional ISA with a different provider each new tax year, but can only pay money into one.
* Tax laws are subject to change and depend on individual circumstances. Tax law may differ in a jurisdiction other than the UK.