Physical singularity in the regular spacetime and fundamental length
  It is shown that formally regular solutions in 5D Kaluza-Klein gravity have singularities. This phenomenon is connected with the existence of a minimal length in nature. The calculation of the derivative of the $G_{55}$ metric component leads to the appearance of the Dirac's $\delta-$function. In this case the Ricci scalar becomes singular since there is a square of this derivative. 
Vladimir Dzhunushaliev and Ratbay Myrzakulov