& within a string / parser expects an entity reference

[Akacem Mohammed]

Hello ,

I am using Schemata to parse an xml file. and have among other the following element

<xs:element name="Firmname"> 
        <xs:simpleType>  
                <xs:restriction base="xs:string"> 
                <xs:maxLength value="90" /> 
                </xs:restriction> 
        </xs:simpleType> 
</xs:element>

the firmmname element contains an & charachter for  example: Gmbh & Co.KG
the SaxParser is throwing the following error:

Fatal_Error The entity name must immediately follow the '&' in the entity reference.  
at line:  7

How should I change the definition of my element in the *.xsd file so that the parser 
doesn't expects an 

entity reference

thanks for any help

Mohammed