Why do NaHCO₃ and KHCO₃ have different crystal structures? Why do $\ce{NaHCO3}$ and $\ce{KHCO3}$ have different crystal structures?


We had this in a test today and this got me stumped...

My questions are:


Do $\ce{NaHCO3}$ and $\ce{KHCO3}$ possess crystal structures?
If they do, why should they have different crystal structures, because they are in the same group and must possess almost similar physical properties.
The reason why the crystal structure of $\ce{NaHCO3}$ is face centered and the crystal structure of $\ce{KHCO3}$ is body centered is due to the fact that the cation/anion ratio is different, meaning that certain types of hole are now too small for the cation to fit into them and as a result it must go into a different hole.