It probably is not possible to convert Solidworks assembly file (*.sldasm) to an Inventor file. However you could export assembly files to individual parts in Solidworks (*.sldprt) and then use any of the available SLDPRT to IPT converter. But you need latest versions of Inventor for this, or at least version higher than the Solidworks file.
Convert SolidWorks assembly data to AutoDesk Inventor CAD part.
We found one software available in the database for this conversion.
Microsoft Windows software - convert sldasm to ipt on Windows
A 2D and 3D CAD construction software
Convert from sldasm file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.