If it is HUF property, the mortgage should be for legal necessity of the HUF. As guarantor for the loan of a company Kartha can only bind teh HUF property if it is for family business. Mortgaging HUF property by Kartha for third party laon, cannot be termed as legal necessity, unless HUF is benefited. Karta has no right to mortgage the HUF property if you can establish that there was no benefit to the HUF. You can take the plea of absence of legal necessity.